I figured this'd be an okay post for this forum because it's applicable to most recent versions of MSFS.
I like to start excruciatingly long flights and then leave to go do stuff around the house. It's driven me insane for years how they cancel your IFR flight plan if you aren't there to quickly tackle radio frequency handoffs. I can even be on the other side of the room while it's on 16X FF; and if I do'nt leap and sprint fast enough, it'll cancel my flight plan. We all know that buliding a long waypoint to waypoint plan takes forever, and there's no way to start in the middle with your GPS if you want to reload it. The autopilot will take you all the way back to your first waypoint.
Anyway, down to the meat. I like to fly only the departures and the arrivals. Once you're up to altitude and you have the autopilot set, wait for the first handoff. Acknowledge it, but don't call the next controller. Seriously. Simply fly all the way (while doing other stuff like laundry while the jet speeds enroute) until you're a few minutes from your descent, and then bring up your ATC window. Give it a second to load up the correct center or approach frequency, and then call them up. The game won't skip a beat, and they'll resume as if you've been on an IFR flight plan all along.