The idea of getting two votes a day, splitting the daily allocation in half is prone to abuse. For example, a member delegated 2500HP or sent the hive equivalent and receives a maximum of 100% vote from Precious. To him/her, it is no use to post twice a day for he/she cannot receive more than a 100% upvote daily. Now, if this member reduces the delegation or the hive equivalent, just to receive a 50% upvote, he/she will receive it twice a day. It is not fair to expend half the HP or hives monthly and receive the same total daily upvote that another member, who spent the full HP or hives, receives.
So, instead of using this 12 hours interval, let's make it simple, not abusable and according to what you wrote on the article above:
The member posts today using the tag and receives the Precious Gem. Today he/she will not receive any other upvote from Precious. Tomorrow he/she will receive his/her due upvote, irrelevant if he/she used or not the tag and will not receive any other upvote tomorrow. And that goes on. You write about precious metals, you receive one Precious Gem (you can only have one PG at any time) and you use it the next time you write a tagless post, never receiving two upvotes on the same day.
Of course, if you do not post for a few days, you have Precious's votes accumulating in value, but this does not affect the idea behind Precious Gems.
@buggedout