I voted more than once a day.
We always have a 5+ minute session after the first potty of the day where they get treats for tricks.
They usually have to do at least one trick for their after-dinner piece of banana.
If they get any other treats during the day, they usually have to do at least one trick.
Sometimes I will ask for tricks while out walking for potty, which is only a minute or two of tricks.
Or, if we meet friends or new friends while out and about, I may ask for the dogs to show tricks, usually only a few minutes at most.
When photographing or filming the dogs, I will ask for a lot of sits, downs, stands, stays, sometimes on objects, etc....
Today, I took Sundog to Lowe's and asked for a few tricks in a distracting public setting.
Sundog usually does a hold while I am fixing their dinner. Since I feed raw, this can take 10 or 15 minutes or more, depending on if I try to fit something else in. Sometimes she holds a little metal bucket, a newspaper, a small fabric tote bag, a screwdriver, a pen, or whatever else I might happen to pick up.
Both Barney and Sundog must wait to be released to eat their food.
The other day, I left my retractable target stick downstairs, so Sundog's Dad gave it to her and she brought it upstairs to me. Sometimes we do something spontaneous like that.
Finally, I think I am settling on an every-other-day schedule for a heavy duty training session which lasts about an hour. I alternate between Sundog and Barney. While one trains tricks for a few minutes, the other one is practicing a calm settle lying on the bed or in the chair (don't know if they know that, though

) Sundog in a very busy dog who has an incredible work ethic and really enjoys "doing", while Barney is energetic and has a bit of a jealousy streak, so he enjoys the entire session also.
As you can see, I try to work in a lot of small sessions here and there with a long training session on a more sparse basis. Of course, the schedule is always subject to change.
I would rate Sundog as an 8-10, depending on the type of trick. Some tricks she picks up immediately and we can start working on duration and distance within 1 or 2 sessions. Barney is a 6-8, depending on the type of trick. He gets too excited for some tricks, but that helps him excel at some tricks too.