Your best bet to get the time you need is make a Lobby. I've found Open works best, as Private lobbies in this game have a myriad of issues due to this being the worst version of the game.
If you let the time run out in-game, you earn 3 minutes of Online time. Factor in the 1 minute of waiting on Character Select, and the timer on the stage select, you're looking at around 5-6 minutes per match, barring connection issues.
You also earn time towards this by spectating matches as well.