I currently work as an editor for a daily science news show. We shoot on green screen with a SONY HV-V1U and chromakey with Keylight in After Effects. I work in OS X 10.8 on a Mac Pro with 2x2.4 GHz 6 Core Intel Xeon and 48 GB of RAM. We also use an internal 250GB SSD Drive so we can work as fast as possible, which we do. However lately my timeline has been rendering very slowly. My timeline is structured with big chunks of graphic heavy footage along with the chromakey for the intro/outros of each story which are bridged by 1 simple layer of b-roll and nothing underneath. My sequence settings are HDV1080i60 with a frame size of 1440x1080. I guess my question is simple: what could really cause this sudden slow down in render time? Also I've noticed that sometimes if I quit FCP and re-open, the render times go back to normal, but that is not often the case. Any leads would be greatly appreciated as it is getting harder and harder for us to hit our strict 5PM deadline.
What is your time line settings say under render? What is your final export, meaning what is the final output of your quality?
I never experienced your problem, but I'd try following:
Trash all FCP plist and preference files. Run Applejack on your machine. Use a maintenance software for cleaning out all swap and cache files.
If the problem still occurs, and you need just to see some pre-renders to check effects, consider this: open the Sequence / TL settings (command + 0) and set the render quality or resolution to 50%.