We did not implement an internal door to our garage conversion office. The garage is semi-internal (hangs off the side of the main house). Main benefit being ability to completely sound isolate the office. My wife and kids can be inside having a party and I can still be on important calls etc. Also quite like the work/life separation, shut the door, and done for the night. Never find myself tempted to browse work stuff past 5pm. Swings and roundabouts I suppose, when it rains I get wet going to "work"