FWIW I don't think the Valley code/shaders/whatever its self triggers this.

I can run valley for > an hour depending on luck/state of my box.

One way to get a long run for me is to go into mem sleep, come out and while
nothing else is running run valley. Based on only a few runs like this, I
haven't locked it yet. Randomly starting valley after my PC has been in use all
day may lock withing 10 seconds.

I am not saying mem sleep cures all locks, just seems to make it hard. After
running valley for an hour one time, I mover onto Unreal elemental, several
runs, no lock. I then tried Unreal Atlantis and eventually got it to hang with
that, though it ran through the scripted bit and I had to start flying around
interactively before the hang.

Unreal Atlantis is a bit different/annoying. Different in that it requests more
vram than I have and annoying as it makes a 1.8 gig cache file under
$HOME/.config.

This mem sleep observation may be luck. I also haven't tested some variants yet
like with vblank_mode=0 or cpufreq_ondemand settings. I run valley all maxed
fullscreen - so yet more variables verses what others may be running it with.