Well, it does depend on the person and the hairstyle. I vote for the “get your friend to follow you with a camera” suggestion. I’ve known people over 40 who look great with long hair, and those who really should do something else to it than just growing it out. Long hair can go anywhere from classy to cave-woman.
I grew up with all the middle-aged and older ladies having either short hair or long hair in buns, so long-haired over-thirty-fives come as a surprise to me. I sometimes agonize over when/whether I’ll have to cut my hair–it’s long and I’m 22, but as I age I don’t know how my style will age with me. I still haven’t found a decent short hairstyle, though, so…
I do think that one reason many ladies chop it off, other than, er, ‘societal norms’, is that it’s easier to wash & care for. At least for them.
But, heck yeah, do whatever you want with your own hair! A close friend or SO has the right to comment on it and say whether they like it or not, just as they might tell you that X outfit looks awesome/unflattering on you. You then get to decide how much weight to assign to these opinions, and make the final decision. It’s YOUR head, YOUR hair. And besides, you usually can grow it back out/cut it at some later date, right?
Scarlett67, my friend and her fiance have a similar deal–she likes his hair long, and he likes hers long, so if he won’t cut his, she won’t cut hers, and everyone’s happy. They both look like happy, shaggy hippies some days, but are blissful. 
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Sheesh, this is the first time I’ve seen anyone get banned over a hairstyle debate…
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