So, you can spend hours and hours on Halo, but wrist gets tired after 20 minutes of culling photos? It could be related to fun vs. work, but it could also be related to wrist fatigue.
Hitting the forward/backward arrows and assigning numbers/colors hundreds of time can be hard on your wrist. Compared to say hitting hundreds of buttons while playing Call of Duty. There is a reason for this. The gaming industry wants you at your game controller so they heavily invest in ergonomics R&D. That investment pays off in terms of being able to play for prolonged period of time (yes, I would definitely not play prolonged periods of time if it wasn't for the comfy controller. HA!).
This concept of ergonomic controller cane be taken to the editing process. Here are three ways to use a game controller with Lightroom.