Well, here's my two cents worth.......if you talk to real boatbuilders, they STEAM wood to bend it. It gets hotter and the LIGNIN doesn't soak out or degrade. If bowmakers MUST boil the wood, then boil it for the shortest time possible.
My best advice would be to get some good instructions on steaming and bending boat/canoe ribs and transfer what works to bowmaking. If you look at your water after you boil for an hour, it is probably a nice, yellow brown. That is the lignin from the wood and it is the lignin that holds the fibers together. Personally, I'd rather have it stay in the wood. But, I'm not up to building bent bows yet......
I do, however, bend lots of wood when making violins, Cellos and mandolins and I spray them with water, and bend fast and HOT with a good compression back strap. But, the wood is thinner, that's for sure.
piper