Framesaver is a wax-in-solvent specially made for bikes.
On my commuter bike I spray WD-40 into every frame orifice, and that seems to keep rust in check. I also keep clear a drainage hole in the bottom bracket.
Steel bikes (like any bikes) may eventually break, there are a few well known weak ponts.
Overheated or sharp-edged braze-ons.
Overheated joins esp chainstay to bottom bracket.
Missaligned rear dropouts.
Sometimes internal rust can eat away inside the chainstay.
Good frames can give decades of service with no problems.