PBCS find accounts not used

We are having some performance issues with so many accounts and would like to remove any account that did not have activity in the past years.

Is there an easy way to find accounts that were never used ? We tried to drill smartview but to make sure nothing is left on some lower level dimension we are getting row limit errors..

So wondering if there is a way to find out if a member in the Account dimension was never used?

Thank you,