Rebalance the load when a down server becomes active again

Say you have 10 clients connecting to a virtual server all split between 2 pool members (5 and 5) using least connection members as the load balancing method and source address persistence. Say a pool member goes down and all 10 clients shift to the active pool member, then some time later the recently down pool member becomes active again. However, the 10 clients continue to send enough traffic to keep the source address persistence timer active thus never expiring. How can I dynamically rebalance the servers in this situation without clearing the persistence table?