A good philosophy to keep in mind when writing books is this: you’re not selling the 1st draft. Whatever plot holes, spelling & grammatical errors, or inconsistencies you have in the 1st draft is more or less a moot point, because it’s not the version you’re going to sell. The purpose of the 1st draft is to finish the book. Get that foundation set, and then once you do, you can roll up your sleeves and do what’s really important: rewrites and edits. That’s where the magic truly happens.
Unlike a first draft, which I believe you should finish within a reasonable amount of time, I urge you to take your sweet, sweet time with the rewrites/edits. You’re applying a fine coating of polish with the rewrite, and you don’t want to mess that up. You want to make sure it’s perfect, or as perfect as you can get it.
Don’t worry about how long it’ll take with the rewrites. If it takes as much time, if not longer, than it did to write the actual thing, well, then, that’s okay. You can’t rush perfection. I finished the Evolution Trigger several months before its actual release, but it took me an almost equal of time just to buff the hell out of it. Huge chunks of it were taken out and changed, and in the end, it came out much better than I could have imagined.