In reply to Walnut: Since climbing is undoubtedly the best fun you can have, why'd you want to choose to give up? Speaking as someone who's 65 goin' on 15, my enthusiasm is undiminished. Of course I can't do what I could even 3 years ago, but the awareness of a limited future can stimulate you to take any opportunity. I can't do strenuous routes to the same degree (I doubt I'll do Kipling Groove again), I can't do as many pitches in a day, I'm less keen to do big walk-ins (or, more to the point, walk-ups) and climbing consecutive days can be a bit of a struggle. But I can still manage the odd VS, mixed in with easier routes, and believe it or not pleasure is to be had doing V Diffs and Severes. There are plenty of those I missed on the way up, so can check them out on the way down.
Incidentally, while I don't regard myself as anything special, when I look at some of the youngsters at the crag SMOKING I think, smugly, you won't still be climbing at my age. To my shame, I've even had the thought out-loud once or twice, but I've bound myself to silence on that subject.