There is no such thing as too much duralac. I paint the mast and the base of the fitting separately, allow it to dry, and carefully mount it so as not to destroy the coating.
I also bed my fittings in sikaflex, as it creates a rubber gasket between everything. Beware though as some silicons and sikaflexs have acid in them that create more corrosion. If you stick with bathroom/kitchen types you should be ok and I haven't had any problems.
You may want to consider; depending on the extent of the corrosion, putting a aluminium sleeve or patch over the mast. The spreaders are a high load point on the mast and you tend to develop hair line cracks between corrosion points. Give your mast a bit of a bend and see if any are evident.
For $260 you can get a new section from Phillip Warren Smith via the association. If you mast does fail and you rips your sail it will cost $100 at least to fix plus any diamond wires/fittings you will have to replace. It might be time to treat yourself to a easter mast and keep the old one as a spare.