When the relationship becomes distant, its goes through a a typical life cycle.
Stage 1 is of deep attachment and missing the loved one. This is when the feeling start to sink in that you are actually not going to meet the person everyday anymore. This usually leads to a steep rise in phone calls (the roadside std/pco and now mobile companies thrive on this). In this stage actually the attachment increases. People frequently wear clothes that were gifted by the other half, or eat food liked by them. Start listening to her/his fav songs or even songs like, lambi judai (the old one) and pyaar kiya to nibhana..
Stage 2 is when you've had enuf of the seperation. There are two ways it goes from here 1. Find a way to re-unite for some time and 2. is when you cant meet the long distance is reeeeeally long - it actually starts to lead to frustration.
1 is fine - coz now you have some few new memories to take along back. (and sing more songs like lambi judai)
2 is frustration. That is when you curse everything including him/her and basically crib and feel the pain and cry. The extreme cases of this also include the "you-dont-love-me-anymore" reaction (I was one of this). But how it goes from here decides if the relation will go on or not.
There are many possible reactions
a). Find a second support system - this is where people discover their "true love". and term the previous relationship as infatuation / passing affair / immature decision / simple "it-wasnt-meant-to-be". Our long distance relationship has just been replaced by a new closer one.
b).Accept the now and wait - this the painful patience - remain committed and hope for the best in future reaction. How long a person survives this depends on a lot of factors - WILL POWER to sustain, TIME given to each other, ROMANTIC nature - yes a romantic person will cherish this pain. But many times a person can start off with b. and later move to a.
The surviving long distance relationships are those where none of the parties have moved to a. till the time of union. The worst case is when both parties are reacting b. but suspect the other of moving to a. That is reeeeally bad. Its like both are paying for nobody's fault.
Stage 3 is when finally the long distance is going to end. (mind it its not ended yet). When the deadline is known, the parties start becoming hopeful again. Its a sweet dreamy stage where its more like going back to stage 1.
I dont have a % but I think few relationships reach till Stage 3. This actually also depends a lot on how long it has been. The longer it is, the difficult it is to reach this stage.
Stage 4 is "wake-up call". Rarely it happens that you will find back the person you left. Time, place, weathers, change.. then how would a person remain untouched. People change as well. Their lifestyle, their like dislikes and sometimes their complete thought processes change. And PHUFF! all the dreams you were seeing for past 2 -3 months go into thin air like that. Its OK. Like they say time is a healer of all.. it teaches you to accept what you dont like and see the brighter side of it. Our long term relationship has just now begun its happily-ever-after journey. Peace and contentment replace passion and Ecstasy.
But sometimes, when people have stayed apart too long, they change, but they expect to see the same younger version that they left back. Sometimes the change is too much to take, especially when the two have changed in two different directions. If there is still time, people usually take the wiser decision of moving on. Its not easy on anyone, but ironically this too leads to the same - Peace and contentment.
-END
Disclaimer: The view expressed are completely judgemental and personal opinion. So please don't try to predict the outcome of your relationship from here. Who knows, you might completely nullify my take on it and redefine a new path :P