Because you want to lock your opponents down with a Winter Orb, I would think you'd want to play it as early as possible: this means maximizing the chance that one of you has at least one in your starting hand.
The chance of getting at least one of two in the top seven cards seems so much smaller than the chance of getting at least one of four in top eight of your deck, it shouldn't help enough that you have two decks..
At least, that's what I think. I'll see if I can find the math to back it up.
Four Orbs in one deck
Out of 386206920 different possible hands of seven cards, provided that the deck has four Winter Orbs, there are 231917400 hands in which you do not hold a single Winter Orb.
So, a 60,05% change of not getting an Winter Orb in your opening hand
Two in two different deck
Per deck, there are 300674088 possible opening without an Orb, so 77,85% percent change.
So, the chance that both decks don't have an Orb in the openinghand is 60,61%
So, a slightly better chance of having one in your opening hand when you don't distribute them..
(I'm such a geek)
