Why do my parents annoy me?

I'm currently 28 years old serving on Active Duty with the Army so my time with my folks is very few and far between. It's actually been almost 2 years since I've spent time with them but we talk on the phone or Skype twice a week.

My question, is every time we talk I get this feeling of annoyance from them. I know they love me and are eager to see me when I take leave, but I think I've developed a sense of emotional separation from them. That's a terrible thing to say but I don't think I like my parents anymore. Hell, I don't even miss them one bit and I feel at this point I could go on the rest of my life without ever seeing them and be content.

I think it all started almost 2 years ago when I visited home and they completely pissed me off by "choking me with attention". After that, I stopped caring. They have also expressed to be taken care of when they get old and just the thought of me looking after them drives me bat sh*t crazy.

Is this normal for me to feel this way? These are the people who raised me and helped make me who I am. Why do I have these feelings of resentment and disregard for them?