stratus, "every couple of hours" is a LONG time.
My surefire bulbs typically last 6 months or so...if not longer. You are only supposed to have it on for a few seconds at a time, so if you factor in that a bulb should last even only 3 hours, thats 180 minutes, which is 10,800 seconds....so, if every "burst of use" is around 8 seconds, you can use that bulb for around 1,350 times...
So long story short, it lasts a while...
Now you can avoid all that by buying a Surefire X200 for example, which uses a Luxeon Star led, very bright, beautiful white light, and lasts forever so to say (10,000 hours is basically forever to me on light usage)