XPS 13 9370/Linux: losing power button and brightness control after a while

Hi, my routine with the laptop is suspending it when done working and resuming/waking up from sleep when I need to use it. It therefore accumulates long up-times along the way, sometimes going week between reboots.

I've noticed that given enough time (typically a week or two, but sometimes just a few days!), the power button will stop working: it will no longer suspend the machine or wake it from sleep. It always goes with brightness control dying (Fn + up/down), but strangely enough, e.g. volume control (Fn + F2/F3) always continues working.

While I can get around it (by accessing power settings for brightness or by issuing a suspend command from the OS), it's obviously quite inconvenient. The problem goes away if I reboot the machine and then comes back a week or two after.

I can live with the problem occurring, but I'd like to not have to reboot the machine to get back brightness control and the power button. Ideally, I'd like to prevent the problem from occurring, of course.

What's wrong and how do I fix it?