Originally Posted by Limbatus .
what is it that makes inside so much better? why are bikes at risk outside if they are stored safe from rain and sun?
Really, it depends on where you are, but the concern ( if there is one) is usually condensation.
If you have a certain amount of humidity, and a certain change in temperature between day/night, you may end up getting condensation on primarily metal surfaces as you go into the cooler hours of the day. And condensation is a regular driver of corrosion.
Inside, you don't have much of a temperature change, so no condensation.
If you're really near the coast, you can also get what's basically salt spray from the sea blown in, which is a real booster for corrosion rates.
Me, I wouldn't worry too much about condensation-driven corrosion. If the bike isn't protected already, it's easy enough to keep on top of that. Salt spray, I haven't had to deal with.
I'd be more worried about risk of theft. Theft from bike racks, storage areas etc are a lot more common than theft from living quarters.