Step 1: clean terminals with a tooth brush and contact cleaner. Make sure you get any green copper corrosion off (it should be nice and shiny).
Tim's tip: I prefer to use an ex girlfriends tooth brush because it makes me laugh
Step 2: put a big blob of Vaseline (petroleum jelly)on terminals.
Tim's tip: most women have a jar of this somewhere in the medicine cabinet
Step 3: melt the Vaseline into the terminals with a heat gun or hair dryer. This helps to coat all the metal parts but won't effect electrical conductivity.
Tim's Tip: don't let it get too hot. You should be able to hold your hand next to the terminals without it burning...if you cant do this it's too hot!
Conclusion: if you do this every few months you will dramatically prolong the life of your sounder. Basically do it anytime you see the green copper corrosion or if it gets sand in it.