I have an Xtracycle, so my bike has an aluminum/steel frame.
I am going into my third winter with the same bike.
I think one of the key things in helping a bike to survive winter weather is unheated storage, sheltered is nice.
It has something to do with preventing condensation, I don't remember all the details, but, it made sense to me, when I read it.
So far it seems to be working.
I basically tend to be at the low maintenance end of the spectrum.
I check the tire pressure weekly, oil the chain as needed. Prevent condensation by keeping the bike outside. Yeah, that just about covers it, for me. Your needs an mileage may vary.