Because of prior bad experiences with adhesive in a Medtronic and a Dexcom CGM, from over 5 to 10 years ago, I assumed that I would need an adhesive patch over the existing Dexcom patch, so bought a couple of varieties, just in case.
This time around, it has all gone well, no irritation, and the devices stay attached for the 10 days. I don’t try to extend the sensor life - I would if I erred in timing the prescription, or one was defective - but in that case, additional adhesive patches would be useful.