Pre grow temperature testing

I have had problems before with temps being higher than expected.

When I did a test run of my last cabinet, I put a thermometer into the tent, covered it with a white sheet of paper, and turned on all my lights for a few hours. I was set with a respectable temperature in the mid 70's. As my plant got bigger, the room got hotter, and I had to upgrade my fan to a pair of better PC fans. By the time I was into mid flowering I was having to open the cabinet when the lights were on to stay below 80*F

I am putting a ton of thought into my next cabinet, because I want to make sure it is as good as I can make it and will last me many years, or at least until I decide to move. I am going beyond acceptable and trying to put as much light in as small of space as possible. When I'm riding the limits like I plan to, I need to try to account for everything. Has anyone had an experience where the plants raised the temperature a noticeable amount? Or, was there some other issue I missed?

As your plants grow they are taking up more space physically so there is less room for air,if that makes sense.

That makes sense, but at the same time I feel the air flow restriction in my grow area is nothing in comparison to my filter, passive intake, or even the wall behind the cabinet the exhaust blows right into. The plant only took half the height of the area, and had ~6 inches between it and each side wall. The area was 2.25x1.25x3 foot with ~160w of CFLs.

Either way, how much of a temp swing has anyone seen due to plants?