Should I keep my girlfriend, who lives in Seattle, when I PCS to Kansas?

I can only tell you of my experience. I had a long distance relationship with my wife for a year before we got married. She lived in Small town in Alabama while I was stationed at Fort Steward GA. During that years we spent as much time together as possible. We just celebrated our 25 wedding anniversary last month. So if you both want it to work out, it can. Good luck and I hope thing work out for the best

Having a relationship takes a lot of work; even more so when you are a service member. The key is communication. Be open and honest with her and yourself. I think it's important to remember that you are still very young and this will be only the first of many times that you will be moved far away from loved ones. If it's meant to be, it will be. Thankfully with technology like Skype and Facetime, keeping that communication line open is easier than it used to be.

That's on you bro. None of us on this site can make that decision for you. The only advice I can give you would be, do you still want to be in a relationship with her at long distance? And how does she feel about it?