Speaking from my own experience in post production, it reminds of the old joke: Q. "How do you eat an elephant?" A. "One bite at a time". You keep plugging away and plugging away at what seems like an impossible mound of work and then at some point you realize you can see the finish line. Once that happens you get a lot more motivated to work more quickly. While I gather Jimm is an extreme perfectionist, I'm sure that at some point he will get to where he can smell the finish line and like a great jockey, sort of goes to the whip to get it done.
One thing I am absolutely certain of: when Act IV is released it will be the absolute best that Jimm and company can make it.