Yeah, longbow archers from the time, using bows in the weight range of 150 to 200lbs, typically had to practice for about 2 hours a day to keep up their strength and accuracy. Skeletons recovered from the Mary Rose, a ship that sank with a compliment of archers on it, shows that many of the archers had fused bones in their backs, from all that longbow usage.
If you're going to shoot casually, 50 lbs sounds great. At 150 lbs and more, you need to be serious about being an archer.