I think the fashion rule to follow in this case is as long as you zip them up (or get someone else to help you, in a pinch) you can wear it. That rule, by the way, applies to jeans, jackets, dresses, and other items of clothing, as well as boots.
Seriously, haven't we demolished these myths about what you can, and supposedly can't, wear at xx age. I'm a big advocate of age-appropriate dressing, but these kind of mindless, blanket "guidelines" make me want to strangle someone. And, I think I'd have a good chance of getting off if I could fill the jury with women of a "certain" age. Just who are these @%*?@ whippersnappers (now there's a nice old lady word, for you) who would dare to tell me what I can, and can't wear!
**Making an exception, though, for Rachylou's vinyl, see-thru, thigh-high boots-- on reflection, probably best to leave anything vinyl, see-thru alone once you are collecting old age cheques.**