Are you sure you're not just used to being exploited? You are, in absolute terms, expending more effort to support these systems "that don't close down", and the question is whether that increase in revenue (indirectly attributable to value you're providing) is being reflected in your pay.

While I agree people in tech have it very good compared to the general populace, having a job that is nicer than most isn't a good excuse for not thinking critically about whether you're being asked for more value than you're being properly compensated for. I have no idea how to quantify the 8 hour work day in terms of output, but it should be fairly unassailable that more hours = more work (should) = more pay.

How about thinking about it this way -- has pay risen (in real terms) significantly since the start of on-call rotations? What happened to the spot for operations people in other disciplines, who normally night shifts and make sure things are running well when the other half of the company is asleep? I think the obvious answer to this question is that you are that ops person now, and you're certainly not getting paid double.