I realize that, but that's like saying car manufactures don't make the fuel so they can't publish MPG.
They should do tests on the fixture to determine the max ambient temperature the fixture (as a system) can sustain and perform the same as their rated specs.
FMEng on the Control Booth forums stated the reflector life would be reduced.
Your car’s life is reduced every time you drive it, too.
The Source Four design is now 26 years old with only very minor changes in that time. They are crammed together near the ceiling in thousands of venues around the world, and most of the original batch of fixtures from 26 years ago are still in use somewhere (my inventory spans several generations and the old ones work as well as the new ones other than some minor optical improvements in newer lens barrels).
Lamps, sockets, and very infrequently reflectors are consumables. Lamps and sockets are very inexpensive. If the areas are reasonably accessible for fixture maintenance, it’s no big deal if your lamps last 1700 hours or 2000 hours. If they are really difficult to access, I suggest that reducing max output to 90% or even 95% will significantly extend the life of your lamps - much more than any ambient temp change.
By the way, you are in the south, so I wonder how much cooler the attic air is than the heat generated by the light fixtures?
RE the skin temperature - I used to have a lot of Strand Century fixtures, and upon migrating to Source Fours, I noticed how much cooler the beam of the S4 was - a major feature they touted. I used an IR thermometer on both fixtures after leaving them on for a while. The Strand skin temperature was something like 225 degrees, while the S4 skin temperature was 350+. This is due to the glass reflector in the S4 that doesn’t reflect the IR of the lamp down the beam, and instead exits through the body of the fixture, which makes the fixture run hotter, but the talent illuminated by the fixture a lot more comfortable.
Source Fours are amazing lights. My only beef with them is the lens barrels - even the EDLT barrels - have such a curved focal plane that using them with gobos makes either the middle sharp and the edges fuzzy or vice versa, whereas mover optics generally have a flat focal plane.