Everyone heals at a different rate. I can work my dick til its red and raw, put some lotion on it and go to bed and it's ready to go when I get up. Other people require longer. It's really just an individual thing, and something you have to figure out for yourself. You will know you're overtraining your cock because it will seem kind of shriveled and hard, like you've fucked once too many times in one day. As soon as you see that it is a good color and kind of fluffed, it's ready to be worked again!