From this study

Treatment of recurrent tendinitis by isokinetic eccentric exercise. (2001)

Diagnosis:  9 Achilles, 10 patellar, and 15 lateral epicondyllar

Outcome:  15/34 patients had complete relief of symptoms, 10/34 had marked decrease in symptoms, 5/34 had moderate decrease in symptoms, and 4/34 had no change in symptoms.

When Assessed:  After 20 to 30 sessions, which should be ~7-10 weeks. Follow up for return to sporting activities was “after 3 months of practice”.

Subjects:  34 patients, 9 Achilles, 10 patellar and 15 epicondyllar. No blinding and no control group.

Protocol:  Isokinetic eccentric exercise 3x per week, 1-5 sets of 10-30 reps, increasing speed and intensity over time. 20-30 sessions. Co-managed with ice, TENS, ultrasound, massage and stretching.

Other Activity:  “Subjects were instructed to avoid provoking pain or discomfort in the course of activities between training sessions.”

My Comments:  

Reported they generally noted a significant decrease in pain by the 10th session. Did exercises just 3x per week to good effect. Found roughly the same effectiveness regardless of tendinitis type.