Chances are there won't be a special this year. There wasn't one last year probably because the exchange rate is so good. If there is one it usually happens in October and it is usually on the 7 day hopper plus. And yes, it usually is a bit cheaper to pick them up at TDS if you can because the exchange rate on the passes is quite good. It's also cheaper to pre-purchase than buy them at the gate. If you are purchasing at TDS make sure you do it 2- 3 weeks before you travel. The reason for this is that although the stores stock the passes regularly, they can sell out and orders can be delayed, especially if you are travelling during high season.