I’ve noticed this too on SU3, after a flight the performance is much lower then if the flight is loaded directly to the destination airport. Sometimes the performance goes as low as half of what it is when loaded directly to the destination airport, in my case in the worst case it causes frame passing issues and perceivable stutters.
I’m running the sim with a 9800X3D, 64gb of RAM and a 7900XT. I reinstalled the sim from scratch but the problem persisted. This problem was absent in SU2.