When I shot target bows, I could shoot any weight, but when I went to only shooting heavy longbows things changed. To shoot a 90# longbow well! I had to work hard to stay in shape. Weights, flex work, bicycling and over a thousand draws and shots a week. The heavy draws required me to draw right or not at all and I think my natural tempo was slower as well. When I would grab a light 50# longbow, my tendency was to jerk it back as fast as the bow shot the arrow forward. The empty bucket amongst the full buckets in a bucket fire brigade, like in an old movie from the 30s. Your brain thinks it is going to take effort, so you throw it in the air. When one shoots a heavier bow, more than just main drawing muscles get stronger. Then when a light bow is drawn, it can be done without using the big muscles and often at a faster draw. I think it is good to have a lighter bow on hand and to shoot it often enough so that your heavy bow form and your light bow form are the same.