Another big parameter is how many people are in the on-call rotation.
If the rotation is spread only on 2 or 3 Ops in the team, well, being on-call every other week, even on reliable systems, can really suck (given you must always make yourself available).
Things can get even worse in periods with a lot of PTOs like Summer or Christmas. During these periods, if the team is small, being on-call 2 or 3 weeks in a row is not uncommon.
If the rotation is spread only on 2 or 3 Ops in the team, well, being on-call every other week, even on reliable systems, can really suck (given you must always make yourself available).
Things can get even worse in periods with a lot of PTOs like Summer or Christmas. During these periods, if the team is small, being on-call 2 or 3 weeks in a row is not uncommon.