CGM Tricks?

I'm on my second CGM sensor. It is the Medtronic Minimed, and I was really looking forward to nursing it along past the three-day time line. But the first sensor gave out on me after 36 hours with a BAD SENSOR alert. Restarting it didn't help.

My second sensor lasted the full three days. So last night I disconnected it, waited ten minutes then tried to restart. After the 2 hour period it told me to calibrate it, and again got the BAD SENSOR alert.

Is there a proper procedure for disconnecting and reconnecting it? I've read a few references to taking off the transmitter an hour before the three days are up. Another about recharging the transmitter, etc. So would love some input from experienced users!