We have a similar story. Married 47 years this year, 39 of which I have been T1D, the Dexcom G4, a pump, and a concerned loving wife who knew the local EMT's by name in the late 80's and early 90's when my control was not so good. The Dexcom and the pump solved those problems but she still wakes up and checks on me when my G4 beeps an alert in the middle of the night.
I offer a grateful thanks to my wife and all the other caring spouses.
Regarding the Dex transmitters and receivers: While I was working the company insurance paid for the Dexcom. After I retired and went on Medicare I started buying directly from Dexcom and scheduled delivery of 1 box of 4 sensors per month; cost was and still is $304/ box. By doing this I receive a free transmitter any time it fails in or out of warranty. I also receive free or very low cost upgrades to G4, G4 Share and G5 (Since they would not give me free transmitters for the power hungry G5 transmitter I declined to complete that upgrade).
My sensors usually last 10 days to two weeks so I often cancel the monthly deliveries; the cancellations have not affected the price of the sensors or the free transmitters.
The latest upgrades each included a receiver that work with the current G4/G5 sensor and both still work fine. I have not had a receiver fail outside of warranty so I do not know if a non-warranty replacement would be free.