Just something I found recently that has given a noticeable boost to my FPS. My PC is about five years old, and I'd been getting around 40-60 FPS on a reasonably simple 85 Dwarf fort. Every six months or so I clean out my case (yes, I still use a desktop), vacuum up any dust-bunnies, blow out the heat sinks with canned air, the standard stuff.
So I went to do this last week and, after all that, I noticed my heat sinks still looked a little... fuzzy. Some wiping got me more dust so I hauled my case out to the shop and fired up the air compressor. A nice point blank blast of 100PSI compressed air knocked a ton more dirt out of the thing, even after the canned air. And I mean a LOT more dirt. I blasted off the rest of my motherboard (with some distance to keep from damaging it) and set stuff back up.
Now that same fort is running at about 55-70 FPS, and a couple other saved forts are also noticeably faster. Apparently a pretty stuck-on layer of dirt had built up on my heat-sink over the years and it was thick enough to cost me some real processing power. I would suggest checking this for anyone whose case is more than a couple years old.
A note for those of you without air compressors: You should get the same level of clean by just wiping, and it probably wouldn't take that much longer. I just like gratuitous use of power tools for small tasks.