Others seem to have adequately answered most of your questions. To sum it up, the FBO owner doesn't know his butt from a hole in the ground when it comes to PLBs.

The replacment life of the lithium batteries is given at a conservative 1/2 their normal life, after taking into account all normal reduction in capacity over time including a self-test at the intervals recommended by the manufacturer, still alowing for a min. 24 hours run time at either -20 or -40 C, depending upon beacon class.

Turn on your PLB as soon as you determine you need help and leave it on.