I'm buying a t-shirt immediately (assuming they sell them, which they should). Back when the Bills were in the Super Bowl every year, my dad never wanted to buy any merchandise because he kept saying we should wait until they win the Super Bowl rather than spend our money on AFC East and AFC Champions stuff. The results were predictably terrible.
Back in 2002, I bought every Angels t-shirt commemorating every Angels accomplishment, leaving me with t-shirts and hats for: 2002 Wild Card, 2002 ALDS, 2002 ALCS, 2002 AL Champions, 2002 World Series, and finally 2002 World Series Champions. It cost a damn fortune but at least I didn't jinx the team.