According to an article in the Kansas City Star, I-49 in Missouri is expected to become official at 12 Noon on December 12, 2012. That would be 12-12-12-12 . I think one should wait and do it at 12:12, so you could have 12-12-12-12-12
Of course, the perfect spot would be Exit 12, but there is no Exit 12. Exit 10 is MO 76 to Anderson, followed by Exit 17: Route B and Route C to Goodman.
That reminds me: I still don't have any I-49 shirts on Cafe Press. I need to work on that (and a hundred other projects). Oh wait: I already DO
On second thought, the news story only mentions a 180 mile section of 71 becoming I-49, I wonder if the Joplin-Pineville segment will be ignored?