No way could I pull a 73 lb bow, but I do practice with a 65 lb bow. I don't do very well with it, but it does build up my strength. Then when I switch to a 60 lb bow to hunt, or a 55 lb bow to shoot in a competition, I find that they are easy to pull and my arrows group much better.
This works pretty well for me, except that with the extra strength I build up, I find that I can hold the 55 lb bow at full draw for a while if I want to. I have to fight the tendency to hold it too long before I release the arrow, because the shot just seems to get worse the longer I hold it.