The load times in co-op are long because the engine has to unload and reload assets for the game to continue. I have had load times of as long as 10 minutes. One idea I thought might be worth sharing is to institute spawn points in the game that are utilized when every player in a game is down. If part of the concern about using this is that enemies downed would remain dead would the dev team be able to track kill counts after checkpoints and spawn in enemies to replace them?