Garry Kasparov had an interesting interview with Indian television where he talked about, among other things, Viswanathan Anand’s reign as World Champion. The topic is very interesting since much is being made of the youth movement in chess lead by a cadre of teens. Kasparov doubts that Anand can keep competing at such a high level against his youthful opponents.
Vishy is a brilliant player. But it is very difficult to compete at 40. He is up against people half his age. I will be surprised if he can go on any longer. He can fight against anyone but time.
I recall Anand saying himself that he would not play as long as Viktor Korchnoi (who still plays at a high level). Kasparov credits the use of computer databases with the ability of younger, more pliable minds to absorb massive amounts of information.