I'm wondering if any body knows what's the average that people have kept the band in?

It is designed to be in for life. It only gets removed if there is an issue.

There are people on this site that have had their bands for more than 5 years.There are other people that have had them for 10 or more years but they are busy living life and they don't visit the support sites as they no longer need them.

Per Elcee's comment the band is meant to be permanent. Unless someone can completely overcome their eating behaviors they would revert to eating too much once the band was removed. It would become like every diet I ever started lost weight and then gave up on.

I am so glad to hear that it is a forever thing. That puts my mind at ease.