[99and04f150]

So my 04 has 36K miles on it and this new mechanic I took it to is saying that my rear brakes are pretty much done. I need new pads and rotors, because if they turn the rotors they will be down to spec. I feel like 36K miles is kinda soon to be doing all this. I am the third owner of the truck, my dad had it for the last 12,000 miles and he drives like an old lady and babies it, I have had it for 3K miles, power braked it like once, just to see what it is like and thats it. I feel like I may be getting swindled here. Any input would be appreciated. Thanks!