My users have been getting call drops at 25 - 30 minutes. In my logs I see
[2013-11-07 09:25:08] WARNING[13264] chan_sip.c: Session-Timer expired - 3be8145a3baef8fa7f4891302fa2796e@MY_SERVER:5060
Is there a value I can change to fix this? If not, where might this issue be occurring? What information should I gather to fix this?
You should also be able to add the lines dpeloquin listed directly into the SETTINGS>Asterisk SIP Settings module section.
I assume this is only happening while you calling out through your SenaWave trunks, they are likely asking for a session-expire and not getting a response back, hopefully this setting will fix that for you.
If it continues to be an issue you can always look into purchase some support credit, and have our techs take a closer look at your logs to try to narrow down the issue.