I've always been out of contact for long periods of time with older members of my family. I hate being unable to talk to my sister or cousin though. I used to be at school with my sister, but with her being older, she left last year, which was the same year that my cousin started, so I was kinda jumping from one family member to the other without meaning to do so. To make up for not seeing my sister anymore since she's off in university now I talk to her on Skype and all that all the time, and I do miss her if we don't have a conversation once in a while.
As for friendships, I find it pretty easy to attach to or detach from someone when I need to without any relationships actually being compromised, at least, not on my end. There are a couple of people I really miss if I don't talk to for a while, though, but generally if I don't talk to a genuine friend for a while then that just means that, well, I haven't talked to them for a while and that's it. In my eyes it doesn't even hint that the friendship might be over, and generally the conversations we have upon talking again are good enough to prove that more or less nothing has really changed at all.
An example is when, a couple of months back, I met up with someone I hadn't seen since very early childhood under very unexpected circumstances but who I remembered quite well for some reason. And after we'd run through all the stuff that had been happening it was like we'd never been apart the whole time. We just started up again really easily and all that.