I've never overhauled a free hub. I've never had issues with one. I have had issues with freewheels on my kids bikes that were left out in the rain.

Do you wash your bike? Maybe just wiping it down would be a better choice to keep from getting water up in the freehub that won't dry out till well after the rust starts..

I find it hard to believe that someone rebuilds their free hub every two or three months. My oldest free hub is five years old and quite a few miles on it. It's never been opened. When It goes bad, I'll be happy to put a new one on it and rejoice that I didn't spend time fiddling with it instead of riding... or posting here at BF when I should be riding. <grin>