Beddding i said bed yes not a typo. You have to bed your brakes. You do some 30 to 4mph slow downs real easy like 10 seconds to do that. there is a write up on se-r.net from Mike about it. If you dont you will not get the best out of your brakes or the life of them. Take them off and see if they are glazed. Cause Im guess you changed pads, bled the system went out on the road floored it to 60 and slammed the brakes on. They bit pretty good then faded. That was green fade. Then you probaly glazed them. What I usualy do to old cars i dont car about
is take the pad and rub it on concrete, close to heavy grit sandpaper
Then go bed the brakes. bedding the back ones just use the hand brake. Thats if you just replace the rears just slow the car down with the hand brake. But dont go like trying to drift or drag them either. Just slow the car down some just like the beding instructions.
Unless you are leaking fluid doubt a rebuild will help. All a rebuild is, is changing the seals inside the piston out and maybe the piston if its boogered up. If you are leaking fluid then yea a rebuild is neccesary. Wouldnt hurt but not like a rebuild alone with improve much. Make sure everything is slideing well with good grease. Make sure plenty of pad left. And rebleed it, I did mine and they were good, Eric did it and it was 10 times better. Sometimes you get a good bleed then sometimes you dont, if you arent an expert at it.