Back in the 90's I worked for an airline that had hot reserve. 'hot' being that you actually sat at the airport instead of at home.
I used to bid reserve on purpose. I did that for a year back in the 90's so I could day trade at home.
Sometimes you will be on reserve say for 12 hours, and then in hour number 11 of sitting around you get the call for a trip that makes your day a few hours longer.