Sam Harris had this interesting take where you should view attention, rather than time, as the primary resource of your life. You are of course upper-bounded by time, but you're also upper-bounded by attention -- if you're not paying attention to anything, you can't get stuff done -- and attention is the smaller and thus more relevant upper-bound.
which means that you should be mindful of your relationship toward notifications. I'm a believer in answering emails super quickly whenever possible, and thus I want notifications. But only for emails that I'm going to respond to. For other people, it may be facebook or twitter or whatnot.
I solve the twitter problem by only following a small number (< 20) of people and reading all of their tweets. This gives a hard upper bound on how much time I can spend on there. Also, about half are almost inactive anyway; in practice, most of it is from ~4 people. And I don't use facebook or instagram