Cisco Application :: ACE-4710 / Conditions For Session-reuse To Work

I try to make session-reuse working on an ACE-4710 Version A5(1.0) without success. Actually, I am facing the problem of the high number of backend HTTP connections that must pass through a firewall. I want to reduce this amount of open sessions with real servers by allowing the ACE to establish permament TCP connections with each rserver.  However, it does not work as I expected. I still see individual TCP sessions established and closed after each GET - 200OK exchange. The parameter-map I have to enable this feature is as follows :
 
parameter-map type http PERF_YHA_HTTP_PARAM
  persistence-rebalance
  set header-maxparse-length 65535
  set content-maxparse-length 65535
server-conn reuse
 
Note : I use PAT, on the backend, as required by the session-reuse feature 

My questions are the followings :How many sessions the ACE would establish with a specific rserver ? only one ? one per TCP option set ?How much time a backend session would last if kept idle for a certain time ?What End Points must share the same TCP options to make sure session-reuse works ? Client to ACE ? ACE to rserver ? all together ?