Our first donor was 32 but had 3 previous successes (4 if you count twins). Our cycle was unsuccessful. After us, she had 3 more successes (4 if you count another set of twins). So for some reason, we were the lone failure. She thinks it may have been due to the fact that our clinic changed her protocol, but we'll never know.
Our second donor was 23 and had 3 previous successes out of 4. She helped give us our twins.
Definitely look for a proven donor first. Whether you love her or not. She is much more likely to follow the protocol and not op out at the last minute.