Correct, its 20 days before an unstarted public league is deleted from the League page. 5 days before unstarted private leagues are deleted.

Started leagues never get automatically deleted. I have manually deleted a few stuck leagues in the past, but I haven't seen any of those in a while.

I do a manual purge of very old games and leagues from time to time to keep the DB tidy.

Note: A lot of code cleanup has happened in the last month. I want to finish that up (cause it's boring but essential), and then I'll start adding new features. A 'tournament' system is on the list, but not at the top. But that might re-write how leagues work.