I've seen alot of references in here regarding long compile times. I want to share with you a little trick I've recently discovered. When my map starts to get big and complex I cover it with a big brush with the aaatrigger texture applied to it.
Work on one section and cover the rest. Compile, test, make changes, and recompile. When your done with that area, cover it and expose the next area you want to work on.
Cuts my compile times in half and I don't have to wait 5hrs to see if something worked.
Cheers