Well, I took mine off as soon as I got my tank. But the saltcreep on the lights are a pian in the butt. I am constantly cleaning them. I may try to put mine back on for the winter but you got to clean them also.....seems like a never-ending job...LOL
There are some heat issues with the glass covers along with oxygen/water mixing. I am going to let someone else really answer this because I have only been doing this for about 10 months myself. This is what I found with my setup.
125 Gal-35 Gal Wet/Dry-Tetra-Tec PF500 HOB
(3) AuquaClear 301 Powerheads-600 GPH
Automatic Tempature Controller
5-6 Inch Sand Bed-200+ lbs of LR