I think I've finally fixed my Vive tracking problems:
First I switched to the link cable. I have my lighthouses mounted to the cheeks of a pair of Ikea book cases, so they aren't mounted as high as they're supposed to be. Sometimes they desync. I thought that might have been the root cause, but it wasn't. It did fix the intermittent desync so I left the cable up.
Next I manually disabled power saving on my USB controllers. That seemed to slow it down - I got about 30 minutes in, instead of 5.
What ended up working, I think, is turning off the Vive camera and unplugging all of my other USB devices. I'll probably play around with it some more to see if I can get away with using the camera, at least. I don't use anything else in VR so there's no real loss.
So if anybody else gets an intermittent grey screen or loses controller tracking, and it won't work again until you reboot the Vive, you should try this stuff.
Got through Bleak Falls Barrow tonight. It's still super cool. Dragons are enormous, it's really something to see an animal that big swooping down at you.