Same boat here. My concert going buddy proclaimed himself "retired" about a year ago. He just takes his teen daughter to Katy Perry, One D, and the like. I managed to twist his arm for Maiden. But that's months away, and he has plenty of time to bail. I've slowed down a lot recently. Just don't enjoy the crowds as much anymore.
Cool side bar: I grew up in Davenport, Iowa (moved to Chicago in '87 for a job). In the spring of '85 I won a contest from the one of the local music stores (Griggs Music) and the local rock station (97 X). The prize? A pair of tickets for every concert within 75 miles of Davenport for A YEAR! Man, I saw a lot of shows that year. Three or four a week wasn't uncommon. And I never drove to any of the shows. It was always, "free ticket if you drive." I made a little money selling the tix for shows I wasn't interested in too. Pretty cool thing for an 18 year old kid in the mid 80s.