I just watched a webinar given by John Hopkins Medicine on the topic of overuse injuries.
The most important concepts that I took out of it, mostly involved the prevention of overuse injuries. Most overuse injuries can be prevented by taking the proper precautions. I have said this before, and I will say it again, listen to your body! Trust it! Believe it!
If you are starting to feel discomfort or pain coming on, you must stop doing what you are doing. You then need to consult either your athletic trainer or a trusted doctor of yours. Trust me when I say that you do not want to experience the wrath of overuse injuries at their worst. Overuse injuries can be the most frustrating experience that you ever have.
The medical doctor that was speaking mentioned the thought that you should take at least 3 months off from your given sport per year. I don't exactly know how this concept is supposed to work for a thrower, but I would assume that it is something to give serious consideration.
She also mentioned that you want to have at least 2 off days per week for your given sport. Rest is very important as an athlete. You may feel that taking 2 days off per week is going to limit your progress. However, if you decide to ignore the 2 days of rest per week and end up with an overuse injury that holds you out for month after month, does your progress really matter?