I’ve found a solution that works for me.
Intel i7-7700K (no OC)
Nvidia GTX 1080ti (factory OC) with 452.06 driver
3440x1440 resolution.
Mix of middle to high in graphics settings in the sim.
Since first start-up of the sim after installation I’ve had CTDs in every session. Sometimes in the menus, sometimes in-flight. Usually after 5-20 minutes.
I noticed that my GPU load was almost always pegged to 98-100% load (using MSI Afterburner).
I wanted to lock FPS to a lower value in the sim without having V-sync on but there is no way of doing that in the sim itself (not that I know of anyway).
I then tried to leave V-sync OFF in the sim and in the Nvidia driver changing Max FPS to 30.
After that I have had no crashes (2 days and 5 sessions 1-2 hours each).
GPU load is now normally in the range 50-80% and FPS locked at 30 (which for me is totally playable).
Using the latest drivers from Nvidia (452.06).
You find the driver setting by having “Adjust image settings with preview” set to “Use the advanced 3D image settings”.
Then in “Manage 3D settings” -> “Program Settings” -> “Microsoft Flight Simulator” set “Max Frame Rate” to 30.
Try it out! It might work for you as well.