[SR-Users] Increase registration expiration time?

Can someone let me know how I can increase the registration expiration time for my endpoint devises? Currently the expiration time is at 60 secs. Thank you. U 2013/07/03 04:39:53.000710 71.252.xxx.xxx:1029 -> 10.164.62.166:5060 REGISTER sip:54.235.xx.xx SIP/2.0. Via: SIP/2.0/UDP 192.168.1.8:5060;branch=z9hG4bKa775b36b50d37b56ad4f012eb8f00401. From: 1003 <sip:1003@54.235.xxx.xxx>;tag=995579843abc595234624. To: 1003 <sip:1003@54.235.xxx.xxx>. Call-ID: 612dd4ee0c06a49fa5b1eff9659d0A1a(a)192.168.1.8. CSeq: 1210 REGISTER. Contact: <sip:1003@192.168.1.8>. Max-Forwards: 70. Authorization: Digest nonce="UdOsRFHTqxj7x8IySw9CzOb1262xg37B",realm="54.235.xxx.xxx",response="122d1065528ac5620b8f0855d30bf297",uri="sip:54.235.xxx.xxx:5060",username="1003". Expires: 60. User-agent: ET747. Content-Length: 0. Arun