The switches themselves aren't really up to the job and often burn out; remove them and examine the state of the pins on the back. If the connector is overheated and discoloured, you'll need a new switch and possibly a repair to the wiring.
IMPORTANT: there is a design fault evident on some cars in this area; the wiring comes out of the switch/connector at the wrong angle, forcing the wire to rub on part of the seat frame, which is very sharp. The resulting short circuit can be disastrous; the wire heats up and melts the insulation, melting into the other wires in the loom under the seat, namely the AIRBAG LOOM. This will burn all the wiring between the airbag ECU and both front seats, as well as possibly damaging the ECU. I have only seen this twice, but that's enough.