I do zero post-workout other than move on to whatever's next in my life.
My "day job" is giving private music lessons, so I have plenty of opportunity to move around. I'm rarely just sitting in a desk chair and working a computer (unless I'm doing my other day job, which is being online here and on StrongFirst's FB pages and groups, but even then, I'm not in one place for a long time).
I always sit with a lumbar support, either a McKenzie roll or just a rolled up towel or sweater. Always, always, always - the very rare exceptions find me being extra mindful of my posture. I'm the guy who, between lifts at the powerlifting meets, has a sweater wrapped around his waist.
No need for back extensions when your workout ends with deadlifts - it tones up the lumbar spine nicely, and the lumbar support keeps the joints from distorting.
Have I answered your question?
-S-