A data-point: Me.

I used to play Everquest. I would describe myself as addicted: I would play so late I had hours less sleep than optimal several nights a week, get up for work tired, go through my work day tired, drive home on the motorway nodding off to sleep (Sometimes I'd have micro-sleeps and swerve. Dangerous!, I must have been crazy!) but as soon as I got home to EQ, I'd suddenly be alert enough to play until the wee small hours again....

I was like that for... over a year, which couldn't have been good, even discounting the risk of killing myself in a crash.

After I stopped playing EQ, (I got forced to quit by circumstances) I played several other MMORPGs over the next few years, culminating in WoW. None of them got me anywhere near as addicted as EQ - maybe my mental immune system had learned to protect me? I dunno, but I do sometimes wish for that 'high' that kept me playing EQ with that intensity, even though I know that it would be bad for me.

I don't know if there's a lesson or a moral in that, but like I said at the top, it is at least a data-point for you.