Sense I started flying RC I have had three electric problems, two switches and one battery. Dirt in a switch once and something came loose in the other switch. The soldered wires on the battery pack had a loose connection. I never lost a plane because of it but two very hard uncontrolled landings did do some damage.
If I have a plane I really like and have put a lot of work, time and money into then they have two batteries and switches. My small planes only get one. The plane I just built has three, one for the ignition too but that isn't a big deal. I use the JR heavy duty switches these days. Other then the dirt in one I haven't had one go bad. The dirty one? Well, flying on a dry lake bed for years with the battery port opened is my problem, bad me!! Because of dumb luck the plane told me it was having a problem with controls kicking around so I caught it before I flew it. My lucky!!