It depends a lot on how "bad" the original footage is. Doing a Let's Play if I'm doing well at my commentary it makes things a lot easier, but if not it can mean a lot more editing to keep things moving. On the short end it can be 15-20 minutes per video, on the longest end, I spent upwards of 6 hours trying to "fix" around 2 hours of footage that I ended up scrapping in the end.