Jumping from 40 to 55 pounds is a huge leap! It also makes a difference what you shoot for a bow. Some have more hand shock, which will tend to exacerbate tendonitis. I have had it in both elbows. What has worked for me is sticking pretty exclusively to my Kanati (absolutely NO hand shock) at #46 pounds. The reduced weight and lack of shock have all but eliminated my tendonitis, and I still shoot a lot. I also tend to shoot several arrows, do something else for a while, then come back and shoot some more.
I can shoot a few arrows from my Mahaska longbow, but if I overdo it the pain returns.The Mahaska is a fine bow but has some shock and draws 55 pounds. I'm not knocking it, but I can't shoot it as much as the Kanati.