Stating the closure date as "months passed since closure" doesn't seem particularly practical.
For questions closed many years ago, we'd end up saying things like:
Closed 92 months ago by Foobar.
If we are not showing the date as we do now:
Closed as not constructive by Foobar Feb 29 '12 at 17:52
We should at least resolve the duration as years + months:
Closed as not constructive by Foobar 7 years, 8 months ago