There may be some overall cooldown timer, but I've found that some blessings are pretty consistent with their cooldown timer. For example, I've always had the "Curious Blessing" be triggered by viewing a thread within the Fair boards after an hour. The "Inspectional Blessing", viewing a profile after 6 hours.I think the cooldown affects all activity overall (rather than just within a category) -- after a certain number of activities are complete, no additional activities seem to net points again until time has passed. So if you wait an hour between making posts but in the middle, have given reactions + voted in polls, it might not count the newest post towards dust. Might be wrong though, but that seems to be what's happening for me.
I always get the most points the first time I participate in forum activities for the day, it looks like.
Might just be coincidence though.
Of course, that said, I don't really have an idea of how the other 4 blessings may work (I'm assuming there's no cooldown for "Acceptance Blessing" since that'd be mean otherwise when it's limited and out of our control, lol). Probably the most annoying one to try and figure out has been the "Democratic Blessing", since I was only able to get it to trigger 3 times during the last window, and the shortest timespan I have between those blessings has been ~17 hours, so it might only be once every 12 hours or something (since I feel like I tried it once after 6 hours but it didn't trigger).