I should share. I've been lucky to usually not be on call except for something unusual, but I've had a few good ones.

Working at the nuclear power plant, first year out of school, we had a mandatory deployment of a new radiation tracking system. Since we were bound by federal regulations, they took effect Jan 1. The actual Jan 1 at midnight. I went to work around 5pm, Dec 31. I went home around 10pm Jan 1. Then worked around 110 hours that week to support an unstable system. Eventually they had to roll back to paper tracking while we struggled with developers that hadn't load tested servers. Got to work 400+ hours that month, roughly going 12on/12off.

The time I was on call was a rotating week for our team of 20 Ops people. I had to cover all Windows, SQL, Exchange, etc. stuff with others on secondary call if I couldn't figure things out. We had to respond to 4 or 5 pages for free, then got paid by the call. I ended up with 30+ pages as we'd just brought on some remote workers on the other side of the world. My first week made some $$, but I slept with an old-style pager on my chest so it wouldn't wake my wife. Needless to say I started to avoid on call after that.