In the beginning of training, I use treats often. Not necessarily always, I use other rewards if I'm not using treats.
As he progresses, rewards are faded for behaviors he's proficient at, but not for new behaviors.
Rewards are never completely eliminated. Even my 9 year old who is trained, proofed, titled and retired still gets rewards.
Rewards can be anything from treats and toys to life rewards ~ being allowed to go outside after he sits at the door, for example.