You don't need to go to failure for your muscles to develop micro-tears. Going to failure may not even be a good idea as it may do more damage than can be repaired in a reasonable amount of time. Take the case of marathon runners... it is inadvisable to run the full 26.2 miles during training as it takes your body too long to recover taking valuable time away from your other workouts.
On the other hand, if you're on steroids, which increase your body's healing rate, then go ahead... go nuts... and be sure to workout every single day.