When we installed all of our Altman 65Q Fresnel instruments this past winter, we used Ushio bulbs. I'm not having really good luck with them. They seem to be a bit "fragile". I am not bouncing the instrument around or anything, I'm just adjusting the angles. I've had to replace two bulbs. I probably have less than 100 hours on the bulbs. Are there "more sturdy" BTN bulbs?