I have also been told that the sensor must wet for 15 minutes before connecting the MM sensor. I just use that time to charge the sensor. The MM sensor works by a gel or substance that is on the probe that sits in the interstitial fluid. Through "trade secrets" glucose will create a measurable reaction when it comes in contact with the probe. The sensor transmits the number of reactions to the pump and the more reactions the higher the ISIG value and the higher your BG is. Conversely, the less reactions the lower your ISIG value and the lower your BG is. This helps explain why sensors expire after some time and need to be calibrated. As the gel/substance on the probe gets used up there are less measurable reactions with glucose for the same BG value. When enough of the gel/substance on the probe is used up, then the sensor will no longer accurately function.
I have also noticed a few things that may help. In the last month I have been using barely expired sensors (don't tell Minimed). After the 2 hour calibration, my ISIG values much lower than they are usually for that BG. A few hours later my ISIG values jump dramatically even though my BG is staying stable. I then recalibrate the sensor a few times and all is well enough (and I even got 6 days out of the last one).
This has made me consider a few things about "wetting and warm-up". I think there could be a preservative/protectant on the probe to keep the gel/substance stable during shipment. This preservative may need to be removed by the body before the gel works correctly? Also the gel/substance may need the warm-up period to start reading (getting reliable ISIG)effectively?
I prefer to start up the new sensor as early as I can to get a good consistent flow of data, too. I would suggest that you try less of a wetting time and see what happens. You will not break the sensor, but make sure your new sensor earns your "trust" before you rely to heavily on it.