Shoulder Work

I do a form of snap pitch that has become quite accurate for me, but after a
day of it working in and around heavy cover my shoulder gets quite sore.
There is no noise or pressure in the joint, but several of the older guys I
know who do a lot of this type fishing have had shoulder surgeries. I hope
to avoid that. My main technique is to fish other methods, but push comes
to shove accurately putting a bait back in the trash produces a lot of big
fish. Any suggestions on methods to improve my technique to avoid this
repetitive motion damage?