Having just rendered a 3 minute project in 4 hours, and wondering why it took so long, I discovered some things that will kill your render speed.
1. Opacity of a track < 100% when you don't mean to.
2. Mismatched media-project settings. I used a DIgital Juice Jumpback file as a background loop. They go into the timeline so easy, you forget that they are 320x240 15fps progressive Indeo codec and your project is 720x480 29.97 interlaced. That's a lot of conversion going on. I took the jumpback file, rendered to .AVI at the proper project settings, and replaced the one in my project with that. (Since I had looped a 5-sec file to 2 minutes, it was worth taking the time to render to an AVI file first and using that.) This cut my render from 4 hours to 2.
3. A track in 3D source alpha mode. I wasn't doing any 3D stuff but had inadvertently set my main video track in this mode. Once I put it back to source alpha (2D), my render time went from 2 hours to 20 minutes.
1. Opacity of a track < 100% when you don't mean to.
2. Mismatched media-project settings. I used a DIgital Juice Jumpback file as a background loop. They go into the timeline so easy, you forget that they are 320x240 15fps progressive Indeo codec and your project is 720x480 29.97 interlaced. That's a lot of conversion going on. I took the jumpback file, rendered to .AVI at the proper project settings, and replaced the one in my project with that. (Since I had looped a 5-sec file to 2 minutes, it was worth taking the time to render to an AVI file first and using that.) This cut my render from 4 hours to 2.
3. A track in 3D source alpha mode. I wasn't doing any 3D stuff but had inadvertently set my main video track in this mode. Once I put it back to source alpha (2D), my render time went from 2 hours to 20 minutes.