As is clear from the responses, I don’t think there is any one-size-fits-all answer.
It depends on whether you want to get through as quickly as possible, or, like me, you want to learn the material as well as you can and let the SRS do its magic. I think the former is easiest with multiple shorter sessions each day. The latter only requires daily (or at least almost daily) reviews and however many lessons you feel you can handle.
It sounds like you prefer a single daily review session. I’d suggest taking a look at your regular schedule and find three potential times when you’re unlikely to be interrupted: say, immediately after you wake up before life starts intruding, just before or just after lunch, and just before bed. Spend ten days forcing yourself to only do your reviews then. After a month, I think it will be clear which you prefer.
I prefer mornings with my coffee. My brain just seems to function best in the morning. I struggle whenever I do my reviews in the evenings.
As soon as they’re ready!
The more you’re awake, the more tired your brain is. So the closer to the time you wake up, the better.
I do them pretty much soon after I wake up. If I’m not fully awake by the time I drag myself onto my computer, I check the forums then start the reviews.
When I started out I used to do them whenever they were available, but after a while I found myself actually getting too distracted by WK, checking it constantly so that I wouldn’t miss those reviews (irregular SRS of the first few levels + some items I didn’t get right getting pushed back making for quite erratic review times).
Now I just do them twice a day for old materials - after I wake up and before I go to bed - and follow the ‘route’ for new materials (for example, 8-12-20-19-18, twice a week, with varying batch sizes). It might not be optimal, but I find that having an established routine helps a lot (which is possible partly because of the current situation, which allows me to have this relatively stable routine, WK or otherwise).
But the best answer is probably what works best for you.