Friends think I'm getting to old to not have a serious relationship yet. I'm 25.

My friends think that I'm approaching that age where I should have had a relationship by now. I'm 25. I've had summer flings but that's about it. I never really thought about it. I am perfectly comfortable not being in a relationship at the moment. But their comments got me thinking....am I really missing out? I just don't think I want to commit to anything. I feel like I've got a lot more living to do. What do you guys think?