Without knowing a bit more about what you are doing it is hard to be certain, but as you call it "topping up" an hour do you have long form content (recorded programmes) that need a bit of music at the end ?
Assuming that is the case, you need to schedule the "top up" music from a group that excludes your Christmas songs.
PlayIt Live has powerful but complex ways of scheduling, in most cases "Clocks" are the way to do it.
Have a look at:
for a start.
Adam King
Hi, i have a folder for Christmas songs, which, obviously, is now not being used. I need this folder to be ignored when topping up an hour, can anyone help, as now im getting random christmas songs being played at the end of some short hours.