Two and a half years to go until I reach youngoldbloke's citical age, no intention of stopping cycling until I'm too weak to get my leg over (as it were)! Not as fast as I was since a load of extra arteries arrived in my chest, but I'm still faster than many of a much more tender age.
Don't wear lycra - don't like the feel of it - ordinary clothes round town and cheapish 'sports kit' on longer rides. I don't care if it isn't the height of fashion on a bike, comfort comes first.
Two bikes I'm happy with, a slicked mtb and a steel tourer, and I've started making the right noises to persuade the family that what I really want for my 60th is another bike. A Surly is the target. It'll take me the next two years but I'm sure I'll get them to understand the n+1 principle in time.
Met a man celebrating his 90th last year. He was pedalling uphill on a recumbent trike, enjoying himself, and probably fitter than many a 70 year old.