Different people is definately different. Some people can go for months and months. We typically get 11~13 days from our Dexcom G5 sensor. So rather than hope we get a good 13 day of accurate data and then find out this sensor gives us crap data at 11 days, if I change it out a couple days before Thanksgiving so we are within the first 7 days for the Thursday and the entire weekend, then I will be able to push the odds into our favor.
In terms of how much time must elapse to increase the accuracy of a sensor, it is likely somewhere around 2 or 3 days (from start of sensor). AFAIK, the accuracy will be better once you have 6 good calibrations in place with the initial double calibration counting as a single calibration. I try to get 6 calibrations within the first 2 days. Then we typically switch to just one calibration per day. Realizing this is neither FDA approved nor recommended by Dexcom. This quickly gets into the larger topic of how best to calibrate a Dexcom.
How to calibrate a Dexcom G4/G5 CGM