From HitExchangeReport.com:
I Love Hits and Web Biz Insider continue to experience sitting balance issues, the only 2 in the current Top 20, August 26 Hit Exchange Report. On average, none of the Top 20 have sitting balances.
No, credits from purchases are not counted and all exchanges are given at least 24-hours to liquidate from current assignments.
Our testing team goal is for liquidation, and therefore each makes adjustments by adding URLs, spreading credits to many URLs, etc. to achieve this goal. We do not expect 100% liquidation and give great consideration before noting any balances. And no, couple hundred hits in balance is no big deal and never noted. What we are looking for is a slow-down, a problem, a noticeable backlog.
A sitting balance issue is most often created by a slow down in surfer activity and/or credit management/a backlog from sales, bonuses, etc.
Read it all at "I Love Hits and Web Biz Insider Sitting Balances"