How long can the sensor actually last?
What surprised me most about this question is the fact that I've not answered it explicitly before. Or rather, that I've not answered it here. I've explained countless times to other folks, on mailing lists, in comments on other blogs and in person, how I prolong sensor life and what my sensor life cycle is, but a quick check of my archives confirms that while I've mentioned it briefly, I've never really explained it here.
So, first the "official answer'. The sensors are designed and approved to last three days. Now that is out of the way we can get in to the real world.
There are several reasons why three day use doesn't cut the mustard for me, not least of which is cost. I'm still not getting any financial assistance for the cost of sensors. I'm told there has been a recent price reduction although I can't confirm as I haven't ordered any sensors recently. I'm working through several "expired" ones I obtained from an acquaintance. [Shh, they are working fine. *knock knock* (on wood).] Previously the UK price was working out close to 50, yes fifty, pounds each. For those of you in the US that is a whopping US$100 per sensor. Every three days? Yeah, I don't think so either.
Admittedly if you have funding or insurance coverage, there isn't the financial incentive to prolong sensor life. But there is another very good reason.
Like a fine wine, sensor accuracy appears to improve with age.
This is purely anecdotal, but it is an observation shared by other CGM users, bloggers included. I find the first three days of sensor data the least accurate of all and so pulling the sensor out every three days would be somewhat counter-productive.
So the unofficial answer to the question is a little along the lines of how long is a piece of string. Personally I use my sensors for two week stretches. I restart* the sensor at days 3 and 6 and it gets up and running again within 15 minutes. On day 7, I disconnect the Minilink and charge it up, leaving the sensor in place. This typically takes 10-20 minutes. On reconnecting there is two hour initialization period and I'm then good to go for another 7 days, restarting on days 3 and 6 again.
But as with everything diabetes, your mileage may vary. Some users have gone much longer. Others stick to shorter time frames. I know one woman who cannot get any usable data past nine days. I stick to two weeks because by that point I'm usually getting the very beginnings of skin irritation. Who knows whether the length of time that I go is damaging my tissues below the surface Sadly the decision on sensor life for me is in a large part economic.
* To restart the sensor at day 3 or 6: go to Sensor --> Sensor Start --> New Sensor and then press ACT. Don't wait for it to ask you for a Meter BG. Just go straight to Sensor --> Enter Meter BG. It will tell you the sensor isn't ready, but press ACT and put the number in anyway. The sensor will pick it up and use it and it stops it alarming to ask for the number a couple of minutes later anyway.
For more about my CGM experiences, see the archives Knowing My Numbers - CGM