If you have had that much of a loss of draw weight in such little time, then i
think there is a problem with your bow. Some longbows are made of inferior
materials and wont hold up long.
Some longbows in the same draw weight will be faster than others at the same
draw weight simply due to the materials used (i.e bamboo vs. hickory). My
suggestion to anyone wanting a good composite longbow is to check out Howard
Hill archery. I've had a HH bow for 10 years now and I think it just shoots
better and better. Also if you are interested in longbows, purchase the 3
volumes of the traditional bowyers bible and start making your own longbows.
Good luck