For whatever reason, I'm a high-stress traveler until I'm through check-in. So I do whatever I can to get checked in and baggage dropped as quickly as I can mange. After that, I'm fine.

Seven years ago:
For international, I used to do four hours ahead - but that allowed me to get out of my office a little early, take trains or buses to BWI from downtown DC, get checked in, eat and head to the lounge.
Three hours at ARN before departure just to make sure I had a little more time with the bearded guy before leaving to head back to the states.

Five years ago:
I realized that most of my time was being spent in the lounge and since I was returning a rental car, I would arrive at BWI three hours ahead, drop off the car then do the check-in, etc. Two hours from departure at ARN was usually plenty to eat and hit the lounge. Plus, because I'd moved, it felt easier to get to the airport at ARN and be on my way an hour to an hour and a quarter ahead (of course, nothing had changed but my perceptions) so cutting a little time there was okay.

Last year:
Changed my airport pair to ARN-EWR (with the drop of BWI from Icelandair). At ARN, we are back to three hours ahead of flight until I can figure out the best timing regarding OLCI and dropping baggage. Seven trips out of ARN since changing to EWR with the occasional IAD thrown in and each one has been wildly different regarding baggage and OLCI procedure. Still haven't chosen a new carrier.
Leaving EWR, because I've dropped the rental car off usually at least a day before, Mom drives me to the airport (an hour from her house). At first she thought 2 hours ahead of flight to plan arrival at EWR was silly, but then trying to meet an incoming flight, she got caught behind an accident on the turnpike and was very stressed at being late. (It's okay, Mom, I landed!)
This last trip, we managed to arrive at the airport 2 hours prior to takeoff - so Mom parked and went in with me to see how it all works for international. Her opinion now is that 2 hours is just barely enough.
My opinion is that I really need to choose a new carrier and get status in a hurry because 2 hours may be fine but I'd sure like some of it in a lounge!