Experienced the same issue with the Asobo 747 (with the Salty Dev mod). The FPS drop was progressive rather than sudden (60 in EDDF, down to 10 or less approaching KORD after 8 hours)
Ran a test flight in Dev mode yesterday and found:
- having a smartCARSs window open cost 10fps regardless. Solution: minimise the window.
- Pausing did not help restore FPS.
- switching from HIGH to LOW graphics settings did not offer any real gain (maybe 2-3) FPS.
-switching off Live Traffic offered up a whopping 30fps in LOW.
In that configurationI held 70+ FPS for over 4 hours and after switching back to Ultra for the approach it held a happy 45fps. (I have a decent mid range spec: 32gb, i7, 2080 etc). And in HD, not 4K.
So unless you are in prison and need the benefit of that view out the virtual window, or have random failures set, I suggest switching down the settings once up in the cruise and going doing something more productive for the next 5-10 hours… Or just accelerate the SIM if you don’t have an ACARS running for your VA… Apologies if this shows a lack of commitment to the immersion!