The problem with the LOA 65 watt fixtures is that it traps heat inside. The fixture is designed to be mounted at an angle, which assumedly means better heat dissipation, when mounted in the down facing position for an aquarium, heat can be a problem for the units longevity. The ballast is solid state and the on board heatsink is is designed assuming adequate ventillation of the housing, which there isn't.
The problem doesn't lie in the angle it's mounted at, the problem lies in the fact that they are designed and constructed to be used OUTSIDE where ballast temps aren't going to go crazy, as they will if you use the unit inside. It helps to drill quite a few holes into the top of the housing to allow heat to escape the ballast area. If you do this, hopefully you'll get a good year or so out of the unit. However, if the ballast is exposed to too much heat, it's going to burn out really prematurely.
"I go right into the aquascaping without any design."