Still have mine (I'm 47), one is sideways, but no cavities, no pain. I have had a few other teeth removed and replaced and crowned, but only when they were beyond redemption. If the teeth are sound, not giving any bother, leave them. My dentist is of the same opinion as me...and he is a very good dentist.
Don't mean to be cheeky, but I grew up in Britain and Australia and frankly there are not a lot of people (specially men) over 70 with any of their own teeth. No fluoride in the water, plus, back then in the services and the general population when teeth became a bother they extracted...sometimes the lot. So the argument the dentist used is flawed.