To manage your timeline render files go to Tools/Render Manager. You can delete renders for specific timelines or whole groups of stuff.

The FCP keeps the cache files around because in many cases it works directly from those cache files. So keeping the cache files around speeds up editing if you ever come back to the project again. Otherwise, FCP will have those horrible red lines and have to rerender, sometimes. Of course it depends on your codec.

Because you use lower-3rds and a lot of neat overlays, those are all rendered and saved into the cache folder. You’ll notice that if you go back to an older episode’s project file, the effects will probably be unrendered (i.e. red line over parts of the video) because you deleted the original cache files. This is okay because you can always rerender those files as long as you have the original video source. Think of cache as a working copy.

At the end of the day, it’s just a tradeoff between space and convenience. I would definitely delete caches after a week and just archive source video, project files, and extra files like episode-specific images.

And now I’m curious, what is Geekbrief’s backup strategy? Obviously you use the lovely Drobo, but do you guys archive to tape? Do you keep every episode? Or do you archive h.264 versions of the episodes and delete the original footage? There are TONS of options and it’s all about what works for you.