Sick Leave is a benefit to be used whenever needed. I make use of that benefit everytime I need it, "even mental health days" I still have close to 1,000 hrs in my balance, and I sure will not leave them when I know that I will not get a penny for those hours if I change jobs or retire from there.
As you said... there is an unwritten rule. Why not write the policy? If the ICU is low census then those are the nurses to be floated. There is no reason to float Telemetry nurses since they are not the ones with low census. I work ICU and absolutely hate to float, but would not wish the same on someone else or bump them. It does not make sense floating two nurses to cover one place. If the reason for floating the ICU nurses is because of low census, give them the choice of floating or taking the day off as vacation or without pay.
Last year the Chief Nurse came around with a cart : cookies and Kool Aid. I asked her to work on giving us a coupon for 12 hrs Excused abcense to be used anytime during the year. (This is what we used to get at another VA.) She said she would check with the director...we´ll see....