I bought 3 of the 8 foot long 4-bulb T8 fixtures from HD some 4 years ago. No covers, just open bulbs which makes bulb replacement quick and easy.
The ballasts were advertised as "cold weather" and I have found that with freezing temps outside and the garage being uninsulated, the bulbs come to full brightness in about 20 seconds. In wearm weather the bulbs come up to full brightness almost instantly.
I'm using Phillips T8 bulbs with a 6500K color temp. The garage ceiling is 9'6" high and painted semi-gloss white along with the walls. It's pretty bright inside!!
The fixtures are mounted so that they run front to back, not across the garage. So far, I have yet to replace a bad bulb or a ballast. I think the fixtures were Lithonia?? IIRC, that was a pretty common brand name at both HD and Lowe's.