I really like this quote by Stewart Brand from his keynote at the IA Summit 2003 (Boxes and Arrows Wrap-up):
Learning (fast) plus continuity (slow) equals robustness and adaptivity.
That basically describes the approach of the most successful associations that I know of. They have a long history and strong identity (continuity) but are always trying to innovate and adapt themselves to a changing environment (fast). The continuity gives them the ability to overcome and adapt the short-term failures that are part of the innovation process.