Simply set up a custom event, on any map, with a 20 mins timer. Select the lawnmower and make sure you set opponents to ZERO. Once you load into your game, you can go AFK for 20 mins. Once the 20 mins is over, repeat the process 2 more times.
Note: If you have your controller wired, you’re good, but if not, the controller may turn off so just pay attention to it.