Sip Trunk register expiry timer

All of this is in Sip.Conf

I have a register string

register => xxxxxxx@sip.broadvoice.com:xxxxx:xxxxxx@sip.broadvoice.com

along with

maxexpirey=3600
defaultexpire=1800
Asterisksiprtautoclear=no

it still have a timeout of 30 sec when it registers.

<— SIP read from UDP:206.15xxxx221:5060 —>
SIP/2.0 200 OK
Call-ID: 5668801c385cxxxxx726d208fb9@sip.broadvoice.com
CSeq: 104 REGISTER
From: sip:xxxxxx5@sip.broadvoice.com;tag=as4xx5947
To: sip:xxxxx@sip.broadvoice.com
Via: SIP/2.0/UDP xxxxxxx:5060;branch=z9hG4bxx5c216f2
Contact: sip:s@xxxxxxxxxxxx
Expires: 30
Content-Length: 0

How do you adjust the register expire timer so it does not try to reregister every 30 sec?
It also does a dnsmgr_lookup for the domain every time too.

Thanks,
Josh