I flew with a guy at ASA a while back who would 'test' his O2 mask until the jump seat was unavailable. That said, he's the 1% compared to the 99% who are great about it. If you're at Express, you might be able to relate to the possibility that they're just overworked and over-stressed by our combined management!
I also had a six leg, min rest day last month where the jump seat was occupied the entire time - we were still friendly, but in the -200 it meant we were adding ballast all day long and just barely making D0 to accommodate our fellow pilot! Again, just trying to say it might be the job and not you and I've heard of no beef our group has with the ExpressJet group!