I have 2 fluorescent 48" t12 40 watt bulbs in some endcaps and powered by a 490XLHTCP MAGNETEK ballast. I have had the light up and running for a few months and have gone through 3 bulbs already. Is this normal? Is there different wattage I need to be aware of? I know little about electricity. Any thoughts would be appreciated. 4500 hour bulbs should last about a year at 12 hours a day per my calculations.