@Yellowdog Please take what I am about to share with a grain of salt. I will simply share my thoughts about what I feel works and doesn’t work in a relationship based on my 40 years of dating and 2 marriages.
First off clingy is not healthy for a relationship and you already know this much. Plus having a long distance relationship is not the best setup to fulfill yours and your GF’s emotional and physical needs. If she is simply insecure or the jealous type IMO there is little you can do to change this. Most women I have found simply want to feel loved, respected, protected and secure in their relationships. If you are able to give her those four things you are golden.
You also mention that it was hard to win her over so I assume you really worked hard to get her. I don’t know what that entailed but whatever you did to get her attention you almost certainly have to maintain. If you have tapered back your efforts to woo her that could be contributing to her clingyness and why you are now having 4 hour phone conversations. IMHO 4 hours is just way too long of time to be stuck on the phone. I had one GF tell me it is not quantity, it’s the quality of the time you spend both on the phone and together.
What else is key to a strong lasting relationship is you! You have to preserve who Yellowdog is and I can’t stress this enough. After every failed relationship I have had I looked back and noticed how I had sacrificed and almost completely abandoned the things I loved to do, I distanced myself from my friends all because I was overly focused, immersed in making her happy and perhaps even clingy in my relationships. I can’t say that if I had behaved differently that those relationships would have lasted. I was younger back then, life and work was a lot less stable and you have articulated that it seems your life is similar in this regard and I think it is healthy that you are able to acknowledge the importance of having a stable career before you are able to commit to your lady. You also have to make sure she is also being true to herself and if you sense she has backed away from the things that are important to her encourage her to do the things she loves to do.
I don’t have a magic answer on how to get your girlfriend to be less clingy other than to talk to her. Express your concerns about this aspect in a loving caring way. Maybe go so far as to share this thread with her. When my wife and I dated we were inseparable, 24 years later we every so often take vacations and weekends alone doing our own thing. And this only underscores how important it is to have a life of your own and her as well so you can feel happy and secure in your relationship and that you haven’t had to sacrifice who you are and what you love to do in life for the sake of a relationship.
Again, this is merely my views I have formed from over 40 years of relationship successes and failures. And these successes and failures were influenced greatly on the time of my life and many of them were at the mercy of fate. Bottom line is you have to be happy in your relationship and if are happy then your GF should be happy as well and if not then this relationship is not healthy for either one of you.