The current level limit is indeed for performance reasons. And it’s very much related to save and load.
Because I can’t save and load, I need to keep all levels in memory (at least the ones you visited anyway). Or every level would restart when you revisit it (retro games might have this for that same reason). Once I can save and load, I can push some levels out of the working memory. Then I can more or less support an unlimited amount of levels.
I’ll add this to the roadmap, so we don’t forget about it: https://trello.com/c/xu7mJhcL