Are y'all still having this issue with not being able to edit after a certain amount of time passes? I've looked in our administrative functions and every member has the ability to modify his/her own posts in general, but there is no separate designation as to time span. If this time limit is a feature of the smf codec and can't be currently changed until some later version, then if anyone needs to modify their post asks the moderators, I'm sure one of the mods will be happy to do so. (With a note, of course, that you requested the edit.)
Jeannie