I do not know the average MTBF of multiswitches, it depends on the amount of exposure, quality of grounding, coax locations, and their exposure to lightning, hours of operation, heat, if it uss an external power adapter, could be the adapter not generating the required power (due to component failure, and is IT surge protected with a newer than one year old surge supressor), water could have leaked in and made a short, etc, did you check to make sure the system is grounded properly (still)? (check for corrosion or breaks or bad contact with grounding wires and blocks), perhaps a nearby strike caused a premature failure due to a flakey ground or water.
Or it was just this switches time to die.