Just last week my Egde 540 has started to take 5 minutes or more to start/open when I plug it in to my PC. It used to open in 10 seconds or less.
Everything is the same. I have found that if Edge540 is just "asleep" it connects quickly. If it is "off" it takes 5 minutes or more. It wakes up quickly to the normal sceeen, and then thinks for 5 minutes before changing to the "connect" screen and filesystem becomes available. It used to connect quickly whether it was "asleep" or "off".