I'll disagree a wee bit.
It's not heat at all ... after all, there is no part of a CFL that gets anywhere near as hot as an incandescent.
UV from the bulb is another issue. Ever wonder why troffer lenses get so brittle? Or why the nice ones are so 'rubbery' and cost so much more than the box-store specials? It's all about the UV.
The UV component of fluorescent lighting plays pure hell with plastics - and is likely part of the reason some folks just don't like fluorescents.
