I've got 2 55 watt PCs on my 29g, and I also thought that after a while they didn't look as bright. But when I eventually replaced the bulbs, after over a year, the new bulbs didn't seem any brighter than the old ones. I remember the tank being blinding to look at when i first upgraded from 20 watts NO to 110 watts PC, but it's not blinding at all now to look at. I'm still not sure if the bulbs are somehow dimmer than before, or if my eyes have just gotten used to it...
-Bob

-Bob