I guess folks don't remember 7666 Hoth Rebel Base. It seems like in the old days, a store exclusive set was available for 6-9 months, then gone for good...the end...that's it...(see 7264 Imperial Inspection
and 7283 Ultimate Space Battle
). These days, it's not so cut and dry. Store elusive sets (whoops...Freudian spell-check)...store exclusive
sets are harder to come by than your average set, sure. But it seems more common these days for exclusive availability to come in spurts. So, 7679 was available before Christmas sometime, then it wasn't (probably because the existing North American stock got bought up for Christmas)...then just after Christmas it came back briefly (probably because of a limited re-supply from some other region, or maybe to save a few bucks they were just waiting to ship more tanks until the new stuff slated for Jan. 2009 release was ready to be sent from production facilities), then it was gone again. Now it's back again. I think it's just a matter of supply distribution.
The other possibility is that the set has undergone a subsequent production run, though I find that pretty unlikely because a)
it's a store exclusive and the retailer probably doesn't want to have to worry about selling more than one production run of the same old set and b)
the set is still retailing for $49.99. And ironically, the status of the set has changed, even as I type, from "Available" to "Call to check product availability".