CHICAGO – Johnny Boychuk considers it second nature when the Boston Bruins are in the playoffs. The aches, the exhaustion, the uncertainty and the pressure of overtime are simply expected. “Oh, we’ve had so many overtimes in the last couple of years,” said the defenseman. “We’re confident going into overtime. We usually come out on top.” He’s right: In the last three postseasons, the Bruins are 11-6 in overtime games, which is indicative of their confidence as a former champion, and the fact they’ve played a lot of extra sessions: 33 percent of their playoff games from 2011-13 went to overtime. It’s even more for the Chicago Blackhawks: Roughly 42 percent of their playoff games in that span went to overtime. “I think it’s helped us. We know what we need to do in overtime,” said Andrew Shaw of the Blackhawks, who won Game 1 in overtime. The Bruins and Blackhawks have played three overtime games in the 2013 Stanley Cup Final, including that triple-overtime classic in Game 1. The notion that they’ll have another one before the end of this series is far from outlandish – it’s the first Final in 20 years to feature three overtime games, and only the sixth since 1927 to have three extra sessions. In fact, if two of their remaining games go to overtime, they’ll tie the 1951 record of five between the Montreal Canadiens and the Toronto Maple Leafs. Play three more, and the 2013 Final will have the most overtime games ever. At this point, are there any butterflies left fluttering before playing in overtime?