When I change my ship-to to a UK address, a lot more stuff shows as available, so it's not that the models aren't out there, it's just that they're in a warehouse in England and not a warehouse in Tennessee. A guy at the local GW shop told me that the practice for the overseas (overseas from GW Headquarters) distribution centers is to let the resin models sell all the way down to zero and base restocks on the number of times logged in customers have hit the "email me when this is available" button. He could have been making that up (he makes a lot of stuff up!).
I started collecting and building on the 40K side, with metal Sisters of Battle, and have found the same periodic droughts in model availability to be true with them. There for awhile I just ordered whatever was available whenever it was available and now have an overly large collection of that army primed and in storage (or in the case of some of the vehicles and my Penitent Engines, unbuilt even). I wonder if I'll get those painted before the plastic sculpts come out!
Right now, though, I'm concentrating on AoS and my Seraphon, across the whole hobby: collecting, building, painting, and playing (I normally include reading in that list, but there's unfortunately not much to read about the Seraphon in current continuity that I haven't read already). And I'm having a blast. Except that I still need that Skink Priest with Feathered Cloak. And some more Razordons. And a bunch more Warriors and Guard. And so on, and so on...