Precisely how long it will take for any particular rider to adapt to a particular bent is impossible to say..it could be 500miles or 5000miles. However, after 1000miles you'll have a good handle on a bent and know how your body is adapting to it.

The important point is that if you are bummed it's hard to climb hills on your bent and you've only got 100miles on it don't despair things will get better with more riding.