With the implication that random reboots of a lesser, but non-zero frequency are okay, it's at least expected?

Odd wording for sure.

If you have Intel wireless or display drivers installed then it is perfectly normal for a computer to randomly reboot.

How often?

I have 495 days of uptime here with intel graphics & wireless.

Reboot your PC mate, the kernel needs updating.

Kpatch?

Not for the scale of changes that KPTI needs, and almost certainly not for the scale of updates they have likely missed.

OpenBSD. I don't think the PTI patches are quite ready yet. Either way I'm not too worried.

Kpatch works on (or has an equivalent in) OpenBSD?

Nope.