Most weekends fill with plans, social commitments, household tasks. A monthly weekend deliberately scheduled with no plans (or minimal) restores in ways busy weekends don't. Spontaneity requires space.
What to do (or not)
Don't plan it. See what you want to do when the day arrives. Sometimes long walk. Sometimes nothing but reading. Sometimes spontaneous outing. The lack of plan is the point.
Once monthly. Most people who try it find one of these weekends per month is among their most restorative time. Plans the other weekends still work; this one different.