PlayStation Network has a limit of around 30 characters but they let you pick something longer. They even send you an email confirming that your password has been updated. But if you try to login with your new password it won't work.
I'll probably forget this within the next time I have to change it. I will then AGAIN try with 128 characters and then 125, 120, 115... while yelling at the emails they send me.
You're absolutely right. I've got a talent for procrastination though. I tried giving myself an excuse while formulating this answer, but I realised that just fixing it would be quicker. Hahaha. Thank you