Wow that was quick... probably a manufacturing issue. The only other thing I've known to blow bulbs quick was too much vibration.
I use the black heat bulbs for some of my other herps at night and the high wattage ones blow after a week or two. Its ridiculous.
Sorry to hear it, I know those bulbs aren't cheap. In my area the only way I can get a new bulb typically is to order one online, which sucks if it is an emergency! I'm real rural and the very few pet shops in a 2 hour radius don't have what I need.
I don't have a cham yet so I'd wait for someone with experience to give you more advice, but when this happened with my bearded dragon and I had to wait like a week for a Reptisun 10.0, I had a flourescent bulb on and I made sure to take him outside when it was sunny and warm enough to bask for anywhere from 30 min to an hour. I was told by a vet that this was the best way because no matter how good the bulb, it will always be inferior to the sun and that an hour in the sun is like a day under a UV bulb. I don't know this to be fact, though, so hopefully someone can clear it up and correct me if I am wrong.