I've repalced 30's a few times too. Also a 50 though that's rare
THe 50's are normally running light (the rig rarley goes over 30 amps per leg it's a 50 amp RV) but the 30's are often running close to spec .
One thing that helps is to treat the plug every time you pull it with DE-OX-IT
De-OX-IT actually reverses corrosion and helps to lift it away. Now one word of caution
De-Ox-it comes in assorted "Flavors' 5, 10 20 50 90 The number indicates the strength of the solution (5%, 10% and so on) and of course the price.
One source for DeOxIt sprayNote that I said it helps. I have yet to find a Cure.
