Even though I'm a big advocate of fast-drafting a first draft, I don't believe in rushing the entire process of writing a novel. Brainstorming my plot and character ideas, for example, will often take months or even years.
Once I finish a fast draft, I'm also not in any hurry to send it off to publishing professionals. Sending out messy, incongruent, unpolished writing will only give you a bad name in the business of publishing, because people in this business are very, very busy.
After a fast draft, I recommend taking some time to clear your head from the project. Generally, my books take over a year from conception to a point where I feel they are ready to sell. Much of that time is due to the process of either head-clearing or waiting for beta readers to get back to me. The best thing you can do for yourself is try to align those two chunks of time.
When you send your book to a beta reader, don't look or even think about it while you're waiting for feedback. And when you receive feedback, unless you're decisively clear about how to take that person's criticism and implement it to make an infinitely-better book, then sit on the suggestions for two weeks and then read them again before making changes. Sometimes our brains need time to rest, and sometimes they need time to digest new directions.
So, yes, there is a time to go fast (I even complete revisions quickly when I'm very clear about what I want to do) but there's also a time to go slow and let your mind have lots of resting space.