Unlike in years gone by there are several ways to stay in touch while in a long distant relationship. (phone, email, text, web cam/skype and of course taking turns flying out to visit one another.) In addition you may also mail post cards and letters from time to time.
You can call each other every morning before heading into work and every night before going to sleep if the time zone difference is not too far apart. If it’s possible make a call during middle of the day or send a quick email to see how their day is going.
However at some point someone is going to have to make a decision to relocate if there is going to be any serious consideration for getting married.
There is no substitute to living within close proximity of one another when it comes to truly getting to know someone as a potential mate for life.
If neither of you can ever imagine relocating then (you know going in your relationship will be ending at some point). It does not mean you can’t enjoy what you have but you have to keep your heart and feet grounded in the reality of your situation.
Best of luck!