YOU'VE got to feel sorry for Mick Jagger. The poor man has made millions, slept with assorted beauties (not all of whom filed paternity suits) and had fun for 58 years. It's a wonder one human frame can take so much.

So where lies the pity? Well, poor Mick's new solo album, Goddess In The Doorway, sold just 954 copies on its first day - despite a slick media campaign which included a freebie documentary on Channel 4. Do you think such a programme might be called a 'softumentary'?

To put Mick's meagre sales in perspective, the buoyant Robbie Williams sold 73,600 copies of Swing When You're Winning in one day. Here is a perfect image of fickle fame, with Robbie impregnable on the dizzy end of the see-saw while the once mighty Mick has rolled to a halt in a nice bed of moss.

Funny that Robbie found true success on his own, while Mick flounders away from the Rolling Stones.

But eventually fame will look through a different window. Robbie Williams steals the moment, but will we still love him in 30 years?

He may find it harder to pull off being a loveable rogue as he approaches 60. Then again, Jagger has stayed much the same since the Sixties. He doesn't even look all that different, turning into a fine porcelain version of his younger self, covered in almost invisible cracks. Tap him and he might fall apart.

As Paul McCartney's new solo album, Driving Rain, has also been released to mostly lukewarm acclaim, this seems a good time to ask if rock stars should quit while they are ahead, rather than dribbling out their years with ever less rewarding albums.

There is a theory that rock music belongs to the young and that the only good rock musician is a young one. In a sense this is true, at least as far as it goes.

I wouldn't lay my life down against this line of argument, but it does leave one question unanswered. What should rock stars do when they get beyond a certain age?

Both Mick and Paul have left the world more musical markers than most, so they could easily let their reputations do the talking. Yet what else is a musician to do but carry on playing?

Others do continue without making fools of themselves. Bob Dylan rumbles on, perpetually in musical motion, and has just produced his best album in years, Love And Theft.

Neil Young has his mellow moments but mostly he rages away, angry, ravaged and still resonant.

Elvis Costello might have produced his best work early on, fitting the template of the angry young songwriter; but he has persevered in restless experimentation, running through country, mock-classical music and a fruitful partnership with Burt Bacharach. All power to him.

Van Morrison was a precocious musical force whose early albums, such as Astral Weeks, Moondance and St Dominic's Preview, alone stand as a testament to his talent.

Yet Morrison, dear grumpy old Morrison, has kept on playing, touring relentlessly when, oddly, playing live seems to pain him.

On a good night, he is a peerless white blues singer. The trouble is, you never know what sort of mood he'll be in.

Which brings me to Richard Thompson, craftsman songwriter, wizard guitarist and charming performer. Most discussions of music do.

Thompson's guitar neck stretches back to the Sixties. And with each year, his music strengthens and develops, reaching new levels of excitement and freshness. In his quiet way, he is a musical marvel.

But he's probably not had as many girlfriends as Mick.