I think it's important to examine your life and decide which things you're doing are positive and which are detrimental to your well-being. As you grow older, you have more constraints on your time and you also know yourself better. Those are going to encourage you to think twice. But there are lots of truly old people on Facebook and whatnot now, so clearly the cost/benefit calculation is different for different people. It's being conservative in the sense that you're trying to conserve your resources and not waste them.

If these fasts sound appealing, I'd say try it. Quitting Facebook, Twitter and Reddit are some of the best decisions I've ever made. On the other hand, I get a lot of value out of leaving feedback on blogs and Slashdot and here. So it's case-by-case for me. Any experiment that helps you know yourself better is at least worth considering and probably worth doing.