Some composers - Verdi, Janacek and more recently Elliott Carter, who was still composing when he reached the age of 103 - have been famous examples of undiminishing flair. Others have retreated into retirement and, in the old days, too many died before they had a chance to decide what to do.
For McLeod, however, the way ahead has been clear.
Born in Aberdeen, he has always been a composer of ability, fleet yet fastidious, who has grown in stature with the passage of time, just as his music has grown in interest.
A new work by him is something to look forward to, and this year there is no shortage of them, along with opportunities to revisit earlier works that have proved their worth.
Today at the Aldeburgh Festival it is something new, his Fantasy On Themes From Britten's Gloriana, which will link him deftly with the festival's founder and with an opera which, by Britten's standards, took a long time to establish itself.
It is one of a series of pieces McLeod has written for the guitarist Ian Watt, who has identified in it a variety of orchestral timbres with which this most subdued of instruments is seldom associated.
Watt has described these as the guitar's "strangest guise" - that of a miniature orchestra. McLeod's opening motif, he says, is like a fanfare. Later, kettledrums can be heard, a scattering of cellos, staccato violins and even a solo clarinet - McLeod's own instrument, which he was taught by Reginald Kell, Jack Brymer and Gervase de Peyer, and for which he has already written a concerto and other works.
Flutes, says Watt, speak in the Morris Dance, which is incorporated in the Fantasy, and a brass ensemble resounds in the Pavane. Coming after the Guitar Concerto, with its hallucinatory Spanish Dance, the new work will show McLeod is still exploring the instrument.
It is a shame the Edinburgh International Festival is not including it, though some of McLeod's music was heard yesterday at the St Magnus Festival in Orkney, when a film for which he composed the soundtrack - Another Time, Another Place - was screened.
Moreover, his orchestral tone poem The Sun Dances is being performed by the BBC Scottish Symphony Orchestra under Donald Runnicles at the London proms on August 3.
An imposing example of Scottish musical colourism, the work marks one of the turning points in McLeod's output, depicting a vision of the sun through the eyes of an old Scottish woman long ago as she climbs Ben More on Easter Sunday.
The changing intensities of the sun were an experience she encountered only once but the colours stayed with her for ever. Towards the end of the work, the strains of the old Scottish psalm tune, Martyrs, steal hauntingly through the orchestra.
While we await the London broadcast, the Scottish pianist Murray McLachlan will be playing McLeod's new Piano Sonata No 5 around the world in a massive tour.
This will take him to Londonderry and Lyon in July; Manchester and Greece in August; Australia in September; and Glasgow, Aberdeen, Stockholm and the International Chopin Festival in Poland later in the year; before closing in Huddersfield, Dundee and Nairn.
Again, it seems Edinburgh, where McLeod lives, will not be hearing it, but no doubt it will get there in the end.
What Edinburgh - along with Glasgow and Perth - will certainly be hearing is a new work entitled Out Of The Silence, which McLeod is composing for the Scottish Chamber Orchestra to perform under Joseph Swensen in January.
Written in tribute to Denmark's great musical maverick Carl Nielsen, it will share a programme with music by that composer and give a glimpse of the imaginative directions in which McLeod's inspiration has recently been running.
He has already issued his Fearful Tales, a macabre send-up of Schoenberg and other members of the Second Viennese School.
Employing a Schoenbergian combination of female semi-spoken voice, viola and piano, this is a brilliant musical evocation of the tale of Struwwelpeter and other scary ditties by Heinrich Hoffmann, heard this year in Scotland and deserving wider performance.
Haflidi's Pictures, for narrator and piano, is something similar - a tribute to his fellow composer, the Icelandic Haflidi Hallgrimsson, a former Edinburgh resident who has a secondary career as an artist and has inspired McLeod to write a sort of modern Pictures At An Exhibition, with spoken comments.
Soon to be heard in Edinburgh is a programme of McLeod's and Kenneth Leighton's organ music, to be given at St Giles Cathedral by Kevin Duggan. This will include the Seven Sacraments Of Poussin, another of McLeod's musical evocations.
But, though he sometimes talks of giving things a rest, he will surely be lured back irresistibly into composition.