I think this all depends on your financial strenght at the time and the repercussions of a call in. If I am sick, yet need the income, I would show up for work. If I am sick, and have a project that must get done, or was to cover for someone else, I would show up. If I thought I might lose my job (especially in these times), I would show up.

There has been times I have worked two weeks straight, without a break. Sometimes you just have to do what you have to do.