I don't consider myself to have a lot of friends, but I'm 28 and virtually everyone I do spend time with is older than me. I got married and had kids young, so married and parenting peers are all older. I own my own web development/consulting business, so my clients and business peers are all older than me. My path works well if you started on it several years ago. If you need a short cut, find any adult fraternal organization to join. Religious and/or service-oriented will probably be most effective. For me it would be the Knights of Columbus or Rotarians, to give a couple examples. I don't know where you are or what exists there, but they can be a great way to meet older people in the parallel- or team-work for a larger cause context that gives people the opportunity to form friendships.
Also, among the reasons older people are useful besides connections is so that you can learn from their wisdom or lack of wisdom. (It can be useful to keep a list for yourself of traits you want to root out and avoid so you don't become that guy 20 years from now.) Usually you can do this learning by active observation on your part, but sometimes people will feel compelled to teach you explicitly. God knows I'm no expert at social graces, but most of the time you probably have to let that ride, and strongly consider the possibility that you deserved it. If you're sure you didn't, try to understand why they thought you did.
Also, among the reasons older people are useful besides connections is so that you can learn from their wisdom or lack of wisdom. (It can be useful to keep a list for yourself of traits you want to root out and avoid so you don't become that guy 20 years from now.) Usually you can do this learning by active observation on your part, but sometimes people will feel compelled to teach you explicitly. God knows I'm no expert at social graces, but most of the time you probably have to let that ride, and strongly consider the possibility that you deserved it. If you're sure you didn't, try to understand why they thought you did.