Well I wont argue since you have actual experience.
Some people haven’t had as much bad luck as others though, recently I talked to Sergey Tyapkin (creator of sci-fi modular environment Sci-Fi Modular Environment in Environments - UE Marketplace ) he says it took about a 100 hours from submission to publication, considering his a real pro at what he does and maybe even the fact that his a bit well known, it makes sense that he wouldn’t go through as much trouble as the rest of us.
Quoting the above message, I’m guessing the cleaner the project the easier it is for everyone.