Back in the good ol' days..... when brake pads were made of asbestos, and various other "hazardous" materials, when the pads got hot, (when you stepped on the brakes hard, or frequently....) they would 'out-gas', and you would lose breaking effectiveness. With todays pad materials, that is pretty much a non-issue for street-driven vehicles. (especially trucks....) The idea behind the slots, or cross-drilled rotors, was to give those gases a place to go, rather than between the pad, and rotor.... making brakes work better. Not really necessary today.
If your rotors are constantly warping, need to find out WHY. If they have been turned down below spec, they won't be very tolerant to heating..... if you have calipers sticking, that will warm them right up too.... rear brakes being out of adjustment will force the fronts to do more of the work, and that heats them up as well.
Time for a thorough brake inspection methinks.