My blinds are closed all the time. I live on the first floor and privacy outweighs any other concern.
If I had reverse blinds that raised instead of lowered and could block the bottom half of the window while letting light in through the top half, I might leave them that way.
There are a couple of weeks in the spring and also a few in the fall when we don’t have to run the HVAC. I have had to run the AC as early as April and as late as December.
Regarding sunlight: Our blinds are sort of translucent, so there is still light coming into the house. But I don’t think I require as much sunlight as some folks, I’d be fine living in a cave.
You probably think I’m crazy, but it makes me grumpy if I’m awakened by too much sunlight. I do much better waking up in darkness or semi-light.
You know how some people throw back the curtain and say “Wake Up!!” ? I hate that. 
GAH!!! Hssssss - the evil daystar, it burnsssssss
I go out for sunlight for about 10 minutes a day - drinking my morning cuppa and watching the chooks works for me.
I do better in the dark - I would have no issue with one of those sleep studies where they shut you in a cave with whatever and wait to see what your circadian cycle does. I pretty much guarantee I would drive them nuts. Give me all the reading material I want, 3 hots and a cot and I would do a funky 2 or 3 hours sleep, up for about 6 or 7 hours, sleep, up, sleep ad nauseum.
mrAru spent 20 years in the Navy alternating sub service and shore duty, he is good with small dark places:D He gets sort of twitchy if there is too much outside around.
I try to be nice about it. When people chirp “Good morning!” I say it back as nicely as I can, while that voice in my head says “What’s so damn good about it!?!?”
