That's not exactly all accurate....high densely growing yew will take a lifetime as Pat, and Eric say. The other option is low elevation yew that takes much less time, it won't be of the same quality, but there are always trade-offs. Elevation, sunlight, temps make for different growth, but will never the less make a decent bow. If you are serious I would prune all the lower branches while young, make sure to seal the cuts to prevent disease......good luck, and if nothing else you would have a special tree that would naturally out live your life time, and several others of your family as well!
VMB