I was wondering how much time I've actually spent playing Hearthstone, but couldn't find any good statistics about average game length. So for the last few weeks I've kept a stop watch with me while I played and noted all my game lengths - I found the results quite interesting.
I've recorded the lengths of 200 arena games over 24 runs with a range of classes - its probable that constructed games would have very different average lengths, and it would be hugely effected by deck type and individual play style. But arena matches should give a fairly middle of the road sample. For each game, I started the clock when I pressed "Play" and stopped the clock when the "Play" button became selectable again after the game ended, so times include the matchmaking process which usually takes 30-60 seconds.
Average game length = 9:49
Class with the shortest average game length - Rogue = 8:55
Class with the longest average game length - Priest = 10:42 (obviously :P)
Shortest games: Paladin vs Warlock = 3:35 (I got a perfect start and the opponent must have had a hand full of high mana cards) Mage vs Druid = 4:15 (Opponent innervated yeti turn 1, mark of nature the wild turn 2 = blow-out) Rogue vs Rogue = 4:15
Longest Games: Shaman vs Druid = 17:00 Mage vs Mage = 16:30 Priest vs Mage = 16:30
15% of games last less than 7 mins. 32.5% last less than 8 mins. 45.5% last less than 9 mins. 56.5% last less than 10 mins. 17% last longer than 13 mins.
I might have expected a normal distribution of game lengths, with the most common lengths being around the average of 9:49, but there was actually a noticeable dip in the number of games around this time. Games seem to fall into two rough groups - ones where one player quickly gains and keeps board control, causing a blow-out win in 6-9 mins - and ones where board control is closely contested into the late turns and where card advantage usually decides the winner in the long run of 11-14+ mins. Tempo vs control. There seems to be relatively fewer games that that fall into the 9-11 mins bracket.
So the answer of how much time I've spent playing Hearthstone? A lot :P