I haven't shot at all for about 2 months. As I work back into shooting, I like to just pull my bows for exercise. I do a couple of sets of 10 with each arm, pulling and holding for about 5 seconds each time. I may do another set of 10 after I'm "worked out", or else maybe 2 or 3 sets of 5. If I feel weak or tired -- maybe just due to a hard day at work -- I just stop and come back to it the next day. I feel that there's no need to push it or hurt myself. I still haven't shot recently, but when I start, I'll be ready for it.
Also, I like to work my bow-draw exercises into a broader regimen of biceps/triceps/shoulder exercises. It becomes another exercise tool for me... instead of a Bowflex, I just draw my bow!