I don't believe that you have to lose friends or closeness, or even stop hanging out completely as you get older. Of course, life takes you into different directions, and some may move far away, but you should still make time for your friends and outside interests, as well. But it also depends on the types of friendships you had, and whether or not they were seasonal.
After a couple of decades of close friendship, you become family, so it's nothing to stop by or include them just as you would family. While the frequency changes, it should never stop altogether, and definitely not if y'all live in the same city. Hell, in this interview Reggie said his circle consists of Doitall & Capri. that he hangs out with and sees. Hell, if women can do it, so can men. And you see it in the older heads that and may hang out at a bar or event or something, the stoop.
Besides, as you get older, you don't do anything but replace the ones that you had. If you're not out solo all the time, then those bar, sporting events, showers, celebrations, after work events with acquaintances, relaxation moments is time that you have for your friends - schedules permitting.