348 days on my warrior, which has been my main since I started playing back in classic WoW. My only "serious" alts are my warlock and my paladin (and they're both still currently sitting at 85; my warrior is my only 90). I have 33 days on the warlock and 24 days on the paladin.
I have rolled one of every class except monk, but all my other alts combined likely aren't going to add up to anything significant (as they're all level 80 or below at this point). I tend to be pretty one dimensional when it comes to classes, and I'm not a big alt hopper. I've pretty much stuck with my warrior through all the times when the class was at its best and its worst. I only rolled the warlock/paladin because my guild had been at points where it was short a healer or a ranged DPS.