After he stopped racing in the Indy cars, Warren's career was revitalized at Oswego Speedway, driving for Tom Heveron in a wingless supermodified.
While subbing for injured driver Doug Heveron, Bentley racked up 5 wins in his first 6 starts which led to a series of great rides including the Flying 5 and one of Paul Dunigan's fleet.
In the early 2000s, Bentley worked with actor Paul Newman in a midget car and supermodified at Star Speedway in Epping, New Hampshire.
In the late 1990s and in the 2000s, Bentley dabbled back in the USAC open-wheel division, and continued to make appearances in supermodifieds.
Later on, sometime around 2007, Bentley's Campground and Biker Saloon were constructed in Arundel, Maine, serving as a tourism site and recreational haven.