Rock ... I ran my Elite 5DSI out of water for an hour or more, more than once, when manually entering GPS coords. I also left the unit on when moving the boat from place to place on the water (tdx is mounted on trolling motor). No ill effects from either of those things were ever detected.
As far as removing the cable from the back of the unit .... if you're careful and gentle, and pull the tdx plug "straight" out from the back of the unit, you should be fine. DO NOT wiggle or bend the tdx plug sharply in any direction to remove it from the unit, and don't "force" the plug into the pin socket !! I did, and bent one of the pins ... and even forced one of the bent pins into the soft plastic of the tdx plug. When I found out the pin was bent, I straightened it back to the correct position so it entered the hole, and the unit worked fine after that. Unfortunately, I did the same thing again (many months later) and when I went to bend the pin back into position ... it broke. Unit is now useless, and has been replaced with a Hook 7. Believe me when I say that I am VERY CAREFUL when plugging or unplugging the unit.