The game seems to have loads that not only get longer over the course of the run but are fairly random in lenght to begin with. Obviously the ideal solution to that would be an autosplitter / LRT.

But since that's not a thing and I'm clueless as to how you even make one to begin with, I have came up with the next best thing, restarting the game every so often. Thing is it's actually fairly complex to test out what the optimal places to do so are and it would also help to know as a rule where exactly the game considers a mission cleared or not to know whether I have to get back to the premission screens or if I can quit right as the "mission clear". For now I'm going with restarting every 20 levels since that equates to 4 restart in a run and even a single one of those restart seems to save enough time to cover for all 4 restarts