Just ran a 20 minute race at RM with the Formula US and all the AI pitted around half distance. Mandatory pit was set to off.
I always race with Get Real setting and with tyres/fuel x1. There were 15 AI set at 105% and I started last on grid.
Yeah, can confirm that they pit with around 7.30 left of the 20 min session. Will see if it is the same on another track.