A TRIVIA question. How many degrees of real separation are there between William Butler Yeats and Keith "Human Riff" Richards? Both wrote a few nice verses, both had (have) interesting careers, yet both managed somehow to wind up venerable and - let's spare the euphemisms - mad.

Yeats said that Byzantium was "no country for old men". Under Ben Bulben's frown, the great poet wrote: "Many times man lives and dies/ Between his two eternities." Keef tells us, for diversion, that he snorted his late father's ashes with a bit of Colombian Charlie for seasoning. There's found art, Melvyn. Call it an intimation.

Mortality fascinates as age advances. Richards may have been joking, in claiming to have ingested his own paternity. Yet how better to promote yet another world tour? Yeats and his poem - the professors can mark me down for this - may have confused declining sexual potency with mythic qualities. The central facts are these: we have not got the hang of ageing, or age, in this modern world.

The process is odd. An entire quarter of a century ago, unbelievably, I was making those young-person, pop-column jokes about "the Rolling Bones", "the Beach Grandads" and the best career move Elvis ever made. I was attempting to suggest that if pop music isn't the preserve of the young it isn't worth the bother.

My mistake. When money is waiting to be made, "Keef n' Mick" - and the rest - will be available to shake their head wounds and donor cards in the general direction of the stadium throng. The withered punters pay up regardless, apparently.

This is a two-fold thing. Part of me once believed that my creaking generation would lose patience, finally, with the Stones, or with The Who, or with whoever was cashing-in this week and promising to die before they got old. Not a bit of it. It turns out that suburban gits will not easily relinquish the right to make a spectacle of themselves for a very expensive gate fee.

"Mick n' Keef" sell out in every venue anywhere that you could name. Get the last two Beatles back together and you will make a billion, guaranteed. Find Elvis and you could settle the national debt for three major economies. But why?

The last time I saw the Stones they were scarily efficient. Nobody in "the band" dared to be "out of it" when the accountants, the persons in black, were watching. This was corporate, slick, programmed. And creepy. But what was the truly funny part?

Elderly men posing as teenagers, or the fact that I would have been happier watching Grand Designs - nice worktop - than reviewing "the greatest rock and roll band in the world"? Neither, actually.

My son, teenage then, was very keen to witness the last, shambling remnants of The Rolling Stones. I had press tickets, very good seats, and the frauds were on his list. I should explain. This was the once-famous (in our house) "See Them Before They Croak" list. He's been ticking off the legends, one by one, for years. Only Dylan has remained elusive. I suspect I might be next.

The point is mundane: old. Really old. Those young people, if they even care, wish to know what we thought we believed we were once talking about. The honest answer is that I'm still not sure. I only know that "old" isn't what it used to be and that ageing, or the refusal to age, is altering our world in ways that we have not yet begun to understand.

Who got old? Couldn't be me, who once saw little Joe Strummer offering a ruck in the bobbing, glimmering light of a sweating hall to the next speed-head who fancied a gob. Couldn't be me, who one night told the same little raghead Joe that no, actually, the girl was my guest, not his.

Strummer's dead, and dead too soon. Life - and death - go on. And nostalgia is despicable, always.

You only really grow up when death becomes real. You become your parents. Somehow you catch the tone and the mood. Your "duty" - who put my name on this list? - is to keep the little ones safe, always. But that's it, really. Then you're old. Then you're dead. Sorry, kids.

Nobody ever cared for those facts. These days, though - the paradox doubles as a joke - our horror in the face of ageing seems almost juvenile. Sixty is the new 40, or some such tosh. It isn't. In my memory a working man got to 65, if he was lucky, kicked around the allotment for a couple of years, and took his leave. Today, we contemplate seriously the possibility that our years in retirement could approach the duration of our years in work. Such a boon was once unimaginable, but are we wiser, more graceful? Not if a guitar player with The Rolling Stones is anything to go by.

Medicine allows us to survive. It does not help us to adjust, personally or collectively, to the implications of a longer life. Certain mature persons insist on behaving like teenagers, for one example. Certain teenagers resent the fact, quite rightly. And certain politicians, ageing before our eyes, cannot bring themselves to admit that Western civilisation is old and growing older.

Take last week's relevant example. The Tories were delighted to discover that Gordon Brown was warned by his civil servants, back in 1997, that a "tax raid" would damage the pensions industry. I covered that budget. The truth is that nobody, least of all the number-crunching big-brains newspapers import for such occasions, had the faintest clue what the chancellor had done, or why an obscure tax credit might matter. The fuss only began much later.

It wasn't a fuss over Labour's disgraceful neglect of the state pension, however. Nor was it a fuss over the idea that ordinary taxpayers, incapable of affording private provision, should ever be subsidising the better off. The "scandal" (The Times headline) was that Brown had placed the baby-boomer generation in fear. Suddenly, those tax-enabled golden years no longer looked so golden. Clearly, this was, is, unjust.

The rage did not truly connect with the pensions problem, state or private. Put aside stock market machinations. The real, pending issue for our coddled time involves a collision between the social and the economic.

WE all want to live, and have fun, for as long as we possibly can. Astounding billions flow into the NHS to ensure that this is so. Yet simultaneously the dull folk who do the sums say, simply, that we are all living too long. We, and generations to come, have ceased to be affordable. The ratio of economically active to inactive is falling by the year, across the Western world. Brutally, too many of us are retiring too soon.

In the decades to come the sinecure class - MPs, say - will continue to protect their pension "pots". Their final salary schemes and their free gifts from the shareholders will continue to be secure. The rest of us may have to begin to understand that a longer life means a longer working life. We will have to reimagine much that we take for granted.

Think it through, especially if you have just embarked upon a career. The old gits want to keep the music and the jobs. And the salaries. And the property-market profits. And - for such is the demographic reality - they want the right to choose a government composed of other old gits. Then present our diminishing supply of youth with the idea that an ageing society tends to be somewhat conservative. Why would a bright 21-year-old elect to subsidise all of that?

Perhaps it's time to stop forking out for those over-priced Stones tickets. Give Glastonbury a miss and spare yourself the humiliation. If you must insist that you are not so old, really, accept that you were never owed anything, by anyone. Stop behaving like a generation of indulged eccentrics. Get a job. Then demand a politics that will accommodate a generation of healthy, working, septuagenarians. That's what's known as the tricky part.

The real intellectual problem has less to do with ageing than with the idea of employment. A society full of older people is, bizarrely, youth-obsessed. Keith Richards is 105, at a guess, and entirely youth-obsessed. Such is the madness of old men.

The expression, as best as I can remember, was "grow up".