There are those who quibble about how much credit he is due for how things have panned out for the club since Tony Mowbray was sacked on March 25, 2010. Some debate how much weight should be given to being champions of a league without Rangers. These are the sort of airy speculations which float around a successful manager who has no serious questions to answer.
Lennon could have been another Mowbray, a man who was chewed up by the pressure of Old Firm management, visibly withdrawing and becoming darker and more distant as the stress mounted. Instead Lennon, younger than his predecessor and without the experience of years managing Hibs and West Brom, grew into the position. There have been highs and lows, inspired moments and mistakes, and disgraceful personal abuse to cope with, but essentially Lennon has grown in the role when Mowbray shrivelled. He has handled being the manager of Celtic.
At his media conference yesterday, ahead of tonight's SPFL Premiership match at Partick Thistle, he turned up wearing a suit. Not a suit and tie, but the suit itself was sufficiently unusual to be worthy of wry comment. There's an old joke about someone suddenly turning up in a suit because they have a court appearance; with Lennon the gag was that he must have dressed for a job interview.
One of his former clubs, Nottingham Forest, is in the market for a manager. Naturally the issue was raised. Without presuming he would be of interest to them, he suggested the environment at the City Ground did not appeal. "You see Neil Warnock turning down the Forest job because of presumed interference from owners," he said. "That seems to be more and more apparent in the game now and I'm not convinced it's good for the game.
"These people are putting a lot of money into it and they want to have their say. I'm not saying they necessarily don't know the game but they certainly know business. Football and business are two totally separate entities and I'm not convinced it's the right way to go.
"Neil Warnock obviously got a feel of it with the conversation he had and felt it wasn't the way he wanted to work. It looks like they want a quick fix and that's not always the right way to go about it."
Through all of that was an unspoken appreciation of his working environment at Celtic.
Four years in charge of the club - appointed as interim manager four years ago yesterday and then confirmed on 9th June, 2010 - have moved Lennon towards the twilight of his natural shelf life, at least as far as Dick Advocaat might think.
The former Rangers manager held the reins at Ibrox for three-and-a-half years from 1998 and said that was about as long as anyone could comfortably handle the west of Scotland hothouse. Martin O'Neill, Gordon Strachan, Alex McLeish and Walter Smith, second time around, all sympathised with that view to varying degrees. Yesterday Lennon did too, while also alluding to further challenges and ambitions he wishes to realise with Celtic. "I can understand why Dick Advocaat said Old Firm managers have a shelf life of four years. I think the job is different now. Football seems to be 100mph now on and off the field.
"I look at [Tottenham manager] Tim Sherwood at the minute and I do see similarities to the way I was when I first took the job. Certainly, behaviour wise and with experience you grow into it and are maybe not as histrionic on the touchline as you used to be, but still as competitive as ever. It was the exuberance of being in the job for the first time and wanting to make an impression.
"The hurt still doesn't go away when you lose games and the competitive juices are still there when you're on the touchline. But certainly when you're looking at yourself from the outside there have definitely been changes. I think the manager's job has become more and more difficult because you're under so much analysis, and the social media side of things has really gone into overdrive. And everyone has an opinion. Your personality traits, your tactics: everything is discussed to the nth degree. I'm talking about the people out there in cyberworld who analyse you to death.
"It makes you wonder how Arsene Wenger can do 1000 games at one club. I always look at these managers - Fergie, Wenger, Mourinho - and although they have had great success they have had huge disappointments as well. It always fascinates me how they bounce back.
"It's a pride thing. Your team is you, an extension of you on the pitch. When you lose it dents your pride. And at a big club you are expected to win, the expectation level gets bigger and bigger every year. Sometimes unrealistically.
"In an ideal world we'd be looking at four [league titles] in a row. If I could start again I'd want a different outcome to that Inverness game [Celtic blew an advantageous position in the 2010-11 title run-in by losing in the Highlands] because we'd done the donkey work against a strong Rangers team. I'd like to have that game back or a couple of League Cup finals [defeats to Rangers and Kilmarnock] but over the piece we've got to be pretty content with where we are."