Originally Posted by JOHN @ URI

If they are blue glass style filters then yes, they do solarize & decrease output. Many HP bed manufacturers recommend that you change your blue glass filters every 2500-3000 hrs. (No one ever does this, but check the manuals on the big HP beds & you will see it.)

If you have mirrored glass like Ergoline/UWE, they do not solarize, but they can get burn/heat marks in the glass & this also will decrease lamp output.

Also check capacitors for HP lamps, no one ever does & they can cause many issues with HP lamps.