It depends on where your coach is stored and for how long.
If your coach is stored at home, as mine is, you can keep it plugged in all the time, because you can keep an eye on things.
If your coach is stored remotely, and you don't plan to use it for a couple of weeks or more, remove/disconnect the negative leads on both the chassis and house batteries. A healthy battery, fully-charged, will retain its charge over a long period.
If your coach is stored remotely, and you plan to use it again in fewer than two weeks, just ensure the battery disconnect switches are off and leave it unpowered.
The "two weeks" thing is just a guideline. It depends on how quickly the batteries discharge under the loads that remain connected when the battery disconnect switches are off.
2008 Holiday Rambler Admiral 30PDD (Ford F-53 chassis)
2009 Honda Fit Sport