If you notice, Power Spots all have timers. These timers tell you how long they will be up before they disappear for awhile again. Power Spots are active for 2 days, but we don’t know how long they are inactive before reappearing 24 hours before opening up again.
Keep in mind that this is more of a game play issue with PoGo than a Wayfarer issue, as Wayfarer has no control over how often or even when Power Spots appear. Power Spots can be edited, requested to be removed, or even be unused Wayspots, so in those aspects they are Wayfarer-related, but not in this aspect.
More info on how Power Spots and Wayfarer are related can be found here: