2.5 full downvotes per day, if always waiting for downvote Mana to fully recover.

25% free DV mana pool that uses the greater of the weight from uv or dv Mana pool... Which means that if you left your uv Mana at max, you can also downvote 12 times consecutively at full power and wait around 5 days for DV Mana to recover from that set of actions.