I second the comment about NOT cutting your hair.
That is such a personal choice and I am appalled that people feel they have the right to comment on your style by saying things like "You are too old for hair that long". Incredible!
They wouldn't have the nerve to say it about your clothing choices I would bet, but hair - for some reason is fair game.
I will be 60 in a few months and sporting thick, red, "thigh length" hair and planning to go for knee length just to see if I can do it. Since I wear it in a bun most days people aren't privvy to exactly how long it is so the comments are rare.
On the occasions when I wear it down in a braid (never loose, it would get shut in doors if I did) I usually get several comments a day - but all positive as in "OMG, your hair is so long. It is really pretty"
I haven't given in to the grey yet - waiting for it to be more uniformly white before I give up the auburn shade I have been sporting for 25 years (normally it's blah light brown). I am actually looking forward to having LONG WHITE HAIR.
That can be spectacular!
So go your own way and tell them to chuck it. I actually consider it a challenge when people question my long hair choice (like sister who wears a man's haircut). If they ask "Why?" I say, "Because I can" ... that's why.
PS - You might want to join the Long Hair Community on Facebook - lots of older ladies there sporting some lovely long hair, many of them grey. https://www.facebook.com/groups/389020237837853/