We love our Dexcom

My son (12 yrs) has been using the dexcom 7 since June.  We have not stopped using it since.  He was on the swim team and I wondered how it would do.  With swimming everyday in the summer, it never fell off!  It works too well in that it wakes me up a lot of nights.  The receiver even works thru the bedroom wall such that I can keep it near me when I am waiting for the high to go down and it alarms.  He never wakes up.  After almost 7 years of never knowing what is going on, I can't believe this technology!   I know a few people who have the medtronic one, but they do not seem to use it very much and do not rave about it.  I was just wondering how others feel about it.  How long until I have to replace the sensor or receiver?