The Los Angeles Kings survived a scare and won the 2012 Stanley Cup, as the New Jersey Devils came back from a 3-0 deficit to force a game 6 thanks to the outstanding play of 40 year old goaltender Martin Brodeur. Marty, arguably the greatest goalie of all time who broke Terry Sawchuk's career shutout record (once thought to be unbreakable), put together perhaps the greatest playoff run ever by a 40 year old goaltender, coming 2 wins short of the Stanley Cup. In 2012 Brodeur had 14 wins, 2.12 GAA, and a .917 SVPCT. Prior to the modern era, there were fewer teams, fewer rounds, and not all series were 7 games. It required less endurance to win the Stanley Cup because players did not have to play as many games. That being said, modern medicine and training techniques have extended playing careers farther than what used to be possible.
Over the last 40 years, there have been 3 memorable performances by 40 year goalies. In 2007 a 42 year old Dominik Hasek posted 10 wins, 1.79 GAA, and a .923 SVPCT playing for the Detroit Red Wings. Hasek had better personal numbers, but came up short in the win column as the Wings lost in the Conference finals that season. In 2011 Dwayne Roloson had 10 wins, 2.51 GAA, and a .924 SVPCT at age 41. Roloson and Hasek posted better save percentages, but failed to advance to the finals. Brodeur had a few bad games (including the one where LA won the Cup) offset by spectacular saves at several key moments in the first 3 rounds. Hasek was the oldest in this group, so his defiance of father time has been the most noteworthy thus far.
All 3 of these best performances Roloson, Hasek, and Brodeur have happened in the last 5 years, not the previous 35 years. The NHL went over 3 decades without a memorable post season by a 40 year old goalie (possibly longer, I capped my own research at 1972). Does this mean that we've only just scratched the surface of great 40 year old seasons? There have been many great performances by goalies in their mid to late to 30s, but the 21st century might turn out to be the millennium of the 40 year old.