I have seen a complain about this from top player too and Screep advice to reserve the room to prevent this to happen again.

I'm not sure that they have mention this in the rule or not but there is some related information in Febuary review.

save and reuse path is a bit complicate for me so I only store the result from "Game.map.findRoute" and use it when my creep need to move between room, for the moving inside the room I only try to optimize the minimum creep need in that room instead. and also try to find a way to make them need to move as little as possible

I have this similar kind of script to count for maximum miner that should be allowed in one room and collect it in memory so if I want to save CPU I'll search for drop only on that open space around the source but currently I'm too greedy and just let them search every place in the room

Hi, shouldn't you also count swamp as open space too?