From my experience, with water the total run time is within 10 mins.
In the run in period, suggest to check the 炭刷 every 2-3 mins. I run 4 white pig last time, every motor has different run-in time. One of it is super fast, after 4 mins, the 炭刷 become too short already. Some of them next to run up to 8 mins.