Ian.
I was forced to retire some time ago, on my 60th.birthday, when I wanted to carry on.
Suffice it to say that I still hold a Class One medical and now work in the training sector.
I still teach aerobatics, instrument and multi-engine flying, test fly and examine.
I also ride a motorbike, sail, run (occasionally) and walk (regularly) 10 -15 miles over rough country, because I love it.
Am I not fit enough to do the job ? Indeed I am probably more fit than a lot of present day teenagers.
It is fact that, apart from external hassle, the job gets easy as you get older.
The daft thing is I can now fly with another "unqualified" person but I can't continue, on larger aircraft, when in company with another "qualified" person.
I can still do the former at night and also when the weather is bad.
The bottom line is some will be OK at 70 and some will be useless at 45.
Some will want to carry on as long as a medical allows and some will want (and can afford!) to retire much earlier.
It's just a case of finding some way to assess each situation on merit instead of a blanket ban on pilots who either wish or need to continue over the present limit.
PS. I do wear specs now and weigh a little bit more than when I was 20 !