Application Development Software

I have a situation where we want to delete all revisions of a content item 7 years after activity ceases on the item. The URM disposition action might look something like: wait 7 years after last check-in and then delete all revisions. However, the disposition action runs against the earliest revision rather than the latest revision and in the example above, 7 years after the check in of the first revision everything would get deleted. We could use "delete revision" as the action, but the problem is we want to keep all revisions until 7 years after the last revision (i.e. no activity for 7 years).

Does anyone know of any disposition tricks that I might try to simulate "7 years after last activity?" As always, thanks in advance for the help.