If you are on you 3rd set of bulbs, I would be looking into a wiring issue, probably shorting out to ground. Alternator could cause that too, if the regulator is bad and it is spiking up to too many volts.
-2001 Tahoe original 5.3 4x4 only 435k
-Down to 2 three wheelers
-1985 V65 Magna
-1973 CT70 with 125cc motor