I have exactly 1 receiver for my FM and 1 for my DSM radio. I see no problem in swapping the rx out from car to car as needed. Why waste money just so you don't have to unplug replug a couple or 3 wires (though I admit it's convenient to have more rx). My Fut. FM was $90 with receiver, my Fut. 2.4 Ghz was $100~ with receiver 1.5 yr ago (no servo included for sure).

I'll also admit that in my Summit, using brushless I have not experienced the same glitching using its stock 27 MHz AM radio and I have gone as far as my 2.4 Ghz. I believe it is a mix of circumstances/equipment, since my Rustler and Emaxx didn't do so well.