My guess is you are way overgeared, surprised you get 5-8 minutes. A 3.5T is a lot of motor for a short course truck, even geared correctly I suspect it will be challenging to keep temps in check for that length of time. Overheating will demagnetize the rotor and possibly burn something up, ESC and/or the motor.

Suggest getting a more reasonable motor, perhaps in the 8.5 to 10.5 range, and work on gearing. If you must have insane speed consider a 3S or higher voltage setup, likely need a different ESC and motor to do that.