According to what I've heard from other players who play more than just one game, some games seem to leave all kinds of clutter behind. If you play other games or use your computer a long time before starting AH, a reboot is recommendable - even more so if you also let your PC go to sleep mode. It only takes a minute and you'll have a clean start for each game.
Another thing that caught my eye is the AIO cooler: Not too long ago a customer had issues with his computer freezing and shutting down especially when gaming. A stress test raised the CPU temperatures pretty high so we swapped the AIO to a Noctua air cooler. When inspecting the AIO it seems that it's only half full, you can hear the liquid running in the pipes when turning.