Depends on how you care for the bike. The big enemy is wet, usually from being left outside. Even if it doesn't rain, severe temperature differences can cause condensation. Putting the bike somewhere outside the direct weather will usually prevent most of this; I keep my steel roadster in a simple shed... It's been fine for years.
I made a simple rust-removing tool with a large-diameter dowel.... Cut a slot with a hacksaw and turned (actually carved) the other end down to fit my hand drill. Stick a couple of pieces of sandpaper into the slot so that the "sand" side always faces out...
Whirr away....