I think that his performance this year was kind of out of character, because of the reasons he described. I think his days are numbered but I also think that he will be in better form during next year's tour than he was for this one.
Who knows how well his body will react when he gets into the heavy training in early 04 though. Who knows how much his body will drop off from the age. (how gradual is the performance decline from aging? Is it pretty sudden? (it seemed that way with Indurain))
I remember reading something before the tour started... he said something about how he knows he is not getting any younger... and he knows his ability is (slowly) decreasing... and that it takes him longer to get out of bed, ETC...
About him winning only one stage... I don't see that as meaning much. He only won one stage in the 2000 tour I think.
But yeah, 5 grand tours is enough for anyone, whether they win them all, or just finish them all in 100th place.