I'll say alot depends on how you draw your bow. If you are drawing the bow with your shoulder in a pinched position, you are heading for trouble.
If your are feeling tension in your shoulders, neck and upper back at full draw, you are creating way too much tension. At 21, you are young enough that your body recovers faster. But either way, over a long period you will have issues. If you draw the bow correctly, where tension at full draw is isolated to mid upper back, you'll have less tension on the shoulders. ever wonder why archers have shoulder pain and have to have surgery and such. Hardly anyone complains from back pain from shooting. They key is how you draw the bow, for me its keeping the draw elbow low as I raise the bow, and slowly straighten it back to anchor, My drawing elbow never raises above my anchor. Coming low that way assures far less shoulder movement or rotation.