There are a lot of things to consider before playing Voracious Hydra.
If you decide to play it for its first ability, then you can't really put it out too early. It's better to wait before you get enough mana for a really powerful double counter effect.
On the other hand, if there is an early threat on the board, and you know that the second ability can deal with it, then it would be wise to play it early on, even if you lose the counter value.
In both cases Voracious Hydra will serve you well.