I personally still use my Opo crown at 75 for a few key reasons:
-i am cheap and pamanas are only ~2k on the Fenrir Server
-i am cheap because i dont have any consistant farming methods (i do too much stuff with random LS folks too frequently to find a good farming substance)
-outside of time invested, which isnt much if you get friends to help, its free
-its a fancey little crown
all that aside, eventually when i stop being lazy (yes yes, i know i need to go farm) i will be getting the Demon Helm (+1) and eventually when i start doing Dyna, my fancey Bard Hat, then, with luck, Marduk's (that will be a while off, though /cry)
with all the above reasons given, there is still one other reason why i havent purposefully changed my head piece: i have around 118~120 chr when i actually go out to do stuff (even some +skill stuff thrown in, which i need more of, too T_T) so i have never really had a problem landing any debuffs, or sleeping pretty much anything.
Granted, i dont do tons of endgame on my BRD, i eventually want to. That being said, however, i dont think i would take anything less than Demon Helm +1 to any actual end game activity.
ZNM/ENM type stuff: sure, Opo will suit you
Dyna/Salvage/Ein(not gonna spell it right anyway)/etc: Demon +1 or better
i dont think anyone will look down on you for still wearing it. if you have one, its always good to keep around (like i said, pamanas are cheap and its a decent boost to chr and MP if you need it). But until the 70s, i cant think of many better head pieces.
MANthra BRD75, BST77
almost all other jobs at 40 or better