TRICARE Prime/TRIWEST Question

Hello everybody, Maybe some of you (Military) can help answer a few questions I have about my TRICARE/TRIWEST Prime approval. I was approved to have the Gastric Bypass at Madigan Army Hospital and I have my consult appointment on the 22nd of January, unfortunately my husband will leave for Iraq sooner then expected and I do not have any family in the US that could stay with me for awhile. Now here are my questions: How long is the approval letter good for? (a year, six months etc.) Can the surgeon at Madigan "extend" the approval? Did anybody ever have to apply for a second approval letter with TRICARE/TRIWEST Prime? Did it go through without any trouble? Thank you so much for your help and time! Best wishes, Sandy