If I'm reading the text below correctly, per the Cospas/Sarsat spec, the beacon position can't be updated more frequently than once every 20 minutes.

The beacon shall commence transmissions upon activation even if no valid position data are available. Until valid data is available, the content of the encoded position data field of the message shall be the default values specified in Annex A. The first input of position data into the beacon message shall occur as soon as valid data is available. If the beacon has the capability to provide updated position data, subsequent transmissions of the updated position shall not occur more frequently than every 20 minutes.

If, after providing valid data, the navigation input fails or is not available, the beacon message shall retain the last valid position for 4 hours (± 5 min) after the last valid position data input. After 4 hours the encoded position shall be set to the default values specified in Annex A.

The requirement for cell phones to provide location information and volumes of units involved has had an effect on the development of newer GPS chip sets that acquire the satellites much faster - and use less power to do so. An example would be the newer GPSMAP x versions from Garmin that get fixes faster and in poorer signal environments than their previous version.

This should help newer PLBs equipped with those chipsets report initial positions quicker.