An interesting project - thanks for pointing it out.
I'm not saying that such long-term projects are impossible, just that they are rare due to institutional and human reasons. And because they are rare, we don't have much experience with how to design successful support institutions.
Yes I do agree with you. ACL is just an example of as the devotion of one or two persons can bring unexpectedly successful results. Achieving the same in bigger organisation is a much harder challenge.
[1] http://www.cs.utexas.edu/users/moore/acl2/acl2-doc.html