I have found the issue. 

The problem was my testing procedure. 
I simulated the http connection using telnet to http port but i didnt generated any traffic(requests). 
I repeated the tests using GET requests and the nat session table was replicated almost instant.  


I post the degug messages. 

The NAT replication trigger is the next segment,request in the tcp session. 

Debug messages 

  Telnet from client 

telnet 10.31.73.12 3099 
*Nov  7 03:52:17.071: TCBB2701B60 connected to 10.31.73.12.3099GET / HTTP/1.0
GET / HTTP/1.0
GET / HTTP/1.0




New active 

Becomes Active at 03:52:32,34  

NATGW2#
*Nov  7 03:52:32.700: %HSRP-5-STATECHANGE: Ethernet0/2 Grp 100 state Standby ->            Active
NATGW2#
*Nov  7 03:52:32.701:  IP-ADDR: ipaddr_table_insert_w_tableid() 10.31.71.254, in            global table on Ethernet0/2
NATGW2#
*Nov  7 03:52:34.657: %HSRP-5-STATECHANGE: Ethernet0/1 Grp 200 state Standby ->            Active


new Active listens for ARP requests for the HSRP IP

*Nov  7 03:52:34.658:  IP-ADDR: ipaddr_table_insert_w_tableid() 192.168.153.253,            in global table on Ethernet0/1


The nat session is recreated on the new Active . 

*Nov  7 03:52:34.745: NAT: API parameters passed: src_addr:10.31.71.3, src_port:           0 dest_addr:10.31.73.12, dest_port:0, proto:6 if_input:Ethernet0/2 pak:B072F0A8            get_translated:1
*Nov  7 03:52:34.745: ipnat_api_translated_address_and_port_common, out->in want            IL,OL
*Nov  7 03:52:34.745: NAT: API Translated-Info(1): (src-addr:10.31.71.3, src-por           t:0) (dest-addr:192.168.153.12, dest-port:0)



Thanks all for helping.