I have always done the same, re-using transmitters until they won’t start, and never paid attention either. But if I had done that this time, I would have run out and had no transmitter and no CGM for several days. Which is why I was glad that @Tim12 HAS kept track of it and let me know the last day I could start my transmitter (99 days). If I had had a spare transmitter then I would have used it, but I do NOT have a spare transmitter so my transmitters are always new with brand new batteries.
I used to re-start sensors also, but they are never as accurate in my experience. They ALWAYS start off about 40 points too high, and REQUIRE calibration to get even close to correct value. And a single calibration is not adequate, they need calibration with a high and low number as well. And finally, even once you do get them properly calibrated, the response curve does not match that of a new sensor, so they go out of calibration in several days and need to be re-calibrated before the 10 day restart is up.
A new sensor will sometimes start reporting a bit lower than actual BG, but never off as far as a restarted sensor. And more importantly, I have found that if you give it some time it will usually close in on a value that is close to accurate - if not I will sometimes calibrate, but I prefer to wait it out for a day or so to see if it corrects itself. If you have no choice you can get extra time out of a restarted sensor - but it is not as good as a new sensor in my experience.