Mike,
I wish I could offer more help but if you're 220v, I don't have any experience. I do think it is odd that the bulb is the non-functioning part. We have never sold a bulb to someone who's burned one out, just to those who've been fortunate to break one.
If you're using these in a restaurant environment, are you cooking at a pace that doesn't allow for proper fat evacuation? (meaning emptying the water bowl & re-filling it.) If excessive fat is allowed to drip onto the bulb that may accentuate premature expiration.
Another check would be the ceramic bulb holders. The screws should be hand-tight & snug, but not overly tight, or you will crack them. If they are loose, you might not come up to temp.
Please don't tell me you're trying to fire up all three of these smokers on the same circuit or using extension cords, that would explain a lot.
Best of luck with the restaurant, bringin' good Q to the masses is always a good thing!
http://www.chezbubba.com Ya think next time I check into a hotel & they ask "Smoking or Non?" they would mind?
