fire doesn't start with just heat. you could take a heat gun to a piece of wood and it won't ignite. besides, it would warp to hell before then and i think you would notice that quite easily.
PMB please don't think I'm picking on you .
I just wanted to point out that fire can start when wood reaches it's "Kindling Temperature"
it's how you can start a fire by rubbing two stick together.
yes wood can also ignite by being exposed to heat from a light fixture in the same manner.
if you place a reflector in the hood it redirects the heat and light. paint can help preserve the moisture of the wood.
in essence long exposure of naked wood to light will slowly remove the moisture in the wood lowering it's "kindling temperature " or ignition temperature. also the 'type ' of wood can differ as some have more resin in them