6-12 weeks. Typically, a rotator cuff strain resolves in 6-12 weeks. They are sometimes associated with other injuries that may take longer. Rotator cuff tears do not heal on their own. They may calm down and stop producing pain, but will not heal back to the original position. Healing after a rotator cuff repair takes 12-16 weeks and continues to improve 6 months after surgery.
Good Question. We need a better sense of your diagnosis first. Did you have an injury and are having shoulder pain or have you had chronic symptoms? If you have had an injury to the rotator cuff we need to figure out if this is a strain/sprain without tearing, a minor partial tear, a structural partial tear, or a full thickness tear. http://www.theshouldercenter.com/rotator-cuff-tear.htm each has different rx.
Depends on severity . Most rotator cuff strains will heal in 2 weeks. Pain that lasts longer should prompt a visit to your doctor od an orthopedic surgeon. If you have a significant tear, worst case, you could be in for 6 or more months to recover from a repair of the rotator cuff.