I figure if I'm bored on nights, there's always someone else who isn't or needs help. On those good nights, I'll help the aides out (leaving them sticky notes to let them know that the job is taken care of and that they don't have to wake my patient again) and check to see if the other nurses need anything. Nothing is worse than feeling harried and feeling that everyone else is relaxing and kicking it back but you.
Then, if I've taken care of all my people's needs for the night and have made sure my coworkers are all okay, I start discharge paperwork for the dayshift and start seeing if there is anything else I can do for them -- more research, 0700 meds before they come in (as long as they aren't blood sugar related)... anything to make their jobs a little easier.
I rarely have a completely boring, kickback night. There's always something for me to do.
The one thing I won't do is wake pts up for stupid stuff. In MHO, waking up a pt to change an IV that it is working just fine but is a little outdated is a cruel and unusual. IV therapy is available in the morning. They can take care of it if the day nurse is too strapped for time. If the IV is painful, not working, or comes out, or I have time early in the night (rare), I'll take care of it. But otherwise, I'm really sorry, but I'd probably punch someone in the face if they woke me up to replace an IV that was working perfectly fine. The Hospital isn't the Ritz, but I do want to be at least a little considerate of my pt's sleeping needs. Makes your job easier during the day too if the pt isn't crabby about me bugging him for stupid stuff all night.