I don't game much at all so I can't give a good timeframe myself. I don't see any major performance issues other than an occasional stutter where I feel like there shouldn't be. My wife, on the other hand, occasionally sees performance issues due to throttling after playing her "tapping" games or snapchatting, as others have mentioned. The Anandtech 5x review gives a fairly detailed assessment of the thermal behavior and states the big cores throttle to 633Mhz after 2 min and then shut off completely after 12. I'd say that probably lines up with some of the behavior my wife is seeing.
It's interesting to me that you don't see this aggressive throttling on other 808 based devices like the G4 or moto x pure. This gives me hope that it can be fixed on the 5X.
I think I know the problem. SuperSU creates a backup before patching the kernel. I think you need to delete the backup first and then flash Franco, then SuperSU again.Flashing supersu systemless 2.66 after the official r1 leads to an error. Flashed on top of the wip build. Downloaded it twice, same thing happened.
Edit: tried flashing the boot.img instead of the zip. Then supersu 2.66. Successfully flashed but stuck forever at Google logo.
Going back to wip for now