That is incredibly unlucky!
I would say getting the free-falls on Gonzo's are about the same as most MG slots - something in the 150 - 180 spins region.
They usually pay pretty well too - in fact, I'm pretty sure it uses different reel strips in free-falls - ether that or it's not random...
(I prefer to think it's the former).
Not played Hearts & Tarts much - it's clone of Deck The Halls, which I call "Bust your Balls" because it's just so darned hard to get a decent win - even in the free-spins...
KK