It may be a little late to throw my 2 cents in on this one... but oh well...

Strings rust for various reasons... but consistent playing actually helps strings longevity in the rust department... obviously they will break faster the more time they're bent and so forht... But playing them consistently will keep the oils from your fingers from settling on the strings and causing the early forms of rust which are oxidation and pitting. Also, you might want to get a string lubricant like fast fret or something similar. They come in sticks and sprays just pick whichever one you would like. Treating your strings with this will wipe away any oils that are left behind from playing... and put a barrier of non corrosive oils between the strings and the ambient air. Making strings last longer, making them play faster, and it also keeps your fretboard somewhat cleaner...