Nebulous
Legend
I'm not really sure how to answer. We definitely don't have a fight every session. When we do, it's not often a fight takes a whole (2 hour) session. On rare occasions, we have a balls to the wall drag out fight that will last 2-3 sessions straight over a couple weeks with nothing but combat, but then switch to roleplaying the next month. This also changes campaign to campaign, based on the story. When I ran Forge of Fury from 3rd-5th level, there were 5 PC deaths. It was a meatgrinder, and only one character escaped alive at the end. By comparison, I'm running Strahd for a newbie group and I've gone easy. They're 9th level now and not a single PC death yet. So, I suppose my answer is just "it depends." The numbers fluctuate too much to give it a definite amount.