As I understand it (and I trust someone will correct me if I'm wrong):
Just as a switch rated for a high current can generally be used with a lower one, a switch rated for a higher voltage can be used with a lower one. Only current, maximum voltage, and sometimes AC vs. DC, matter.
Non-electronic wall switches are generally suitable for both AC and DC. (Non-mercury types will wear out faster with DC, since the arcs tend to move the metal the same way every time they're opened, rather than randomly. But that's not usually an issue since the lifetime is decades to centuries. If you're worried, switch the wires every decade or so.)
If a switch doesn't say AC on its label it's suitable for DC.
This does NOT apply to circuit breakers, since extinguishing an AC arc is easier. (It does it for you 100 or 120 times per second and you only have to keep it from reigniting on the next half-cycle). You need to get one rated for DC. Fuses are generally rated for both AC and DC, and again it's just current and max votage that matter. (But check the labels on the giant ones.)