i think the time limit is more than 28 days Vaughan but nowhere actually states an exact time.

meck: one thing i disagree with is that changing priority in ctrl,alt and del only affects the gui not the actual processor but indirectly it does. I can make my client get higher numbers and finish blocks up to 10 secs quicker from having it set high rather than normal under task manager.
Also to clarify when they expire you can still work on them as they are always there but they will also be "recycled" so as a new workunit request is recieved those numbers will be sent again.

the rest is good but maybe put somehitng in about the SOb tool for recovery, makes it much easier then editing registary yourself and is a small and simple but effective application.