I may be misunderstanding this, but that does not appear to be what the Dexcom warranty seems to say. 
I have always focused on the “Use By Date” on the box of the transmitter. I had assumed if the transmitter failed within 3 months after its first use, then the warranty would be effective so long as the failure occurred prior to that “Use By Date”. So I’m astounded to find no mention of “Use By Date” in the warranty.
Instead the Warranty Period is defined as:
the period commencing on the date of first use by the original purchaser (the “Date of First Use”) and expiring three (3) months thereafter; provided, that, the Date of First use occurs within five (5) months of the date of shipment (or disbursement) of the transmitter to you (“Warranty Period”)
What madness is this?
There is only a 5 month warranty which dates from when the transmitter was shipped to, not received by, you?
If you received two transmitters in the same shipment, then one of them will have only a 2 month warranty?
Also of interest is that when you return the defective transmitter to Dexcom, the return package is supposed to include:
- Transmitter
- Sales receipt or comparable substitute proof of sale showing the date of purchase
- Transmitter’s serial number
- Seller’s name and address
- Purchaser’s name and address for Dexcom to ship the replacement
I highlighted two items above because the US VA sends me my supplies. I (usually) have only an online prescription in the VA’s computer system. There is some paperwork that comes with the supplies but I’ve always just thrown that in the recycling. Should I have kept it? 
Now I have never heard of anyone having problems with Dexcom customer service because of the legalese outlined above. But it looks like Dexcom could pull this out of their back pocket and hassle someone big time if they chose to. Huh? 
One other thing. Only the original purchaser appears to be covered by the warranty. So if you got your supplies from anyone other than a Dexcom supply, then technically are you not covered by any warranty? 
This is some special stuff. 