When I'm at home at my desk....if I always have the surface plugged into the wall outlet, will this preserve my battery life over time?
I assume it doesn't matter but just checking.
Generally speaking, that is about all you can do for the battery. That, and do what you can to not let it get hot.
Heat reduces the life, and cycling it reduces the life.
It is actually better for them to be hold at closer to a 50% charge too, but there is no practical way to do that. If you aren't going to use it for a month, run it down to maybe 50%, power it off, and keep it off the charger while unused.
Occasionally, maybe every other month, run the battery as low as possible to recalibrate the battery gauge, if you want. This won't help the battery life though.