One must define what is "making a long distance relationship work."
Do you mean it leads to a marriage or is it just a certain amount of time as in a year, two years, or three years...etc?
The problem with the vast majority of couples in long distance relationships is (they have no timeline or plan for when they will be together permanently.)
(Long distance relationships were meant to be temporary!)
The goal is to be with the one you love!
At some point someone has to make a move. A long distance relationship without “a light at the end of the tunnel” is likely to fail.
How long someone is willing to "drift" in a long distance relationship without an end in sight will vary from person to person. However I'd say around the one year mark you should know if you are willing to relocate or if your mate plans to relocate.
It’s the counting down the months, weeks, and days until you are finally done with the inconvenience of being in a long distance relationship that keeps it strong!
The only reason for being in a long distance relationship is the belief he or she might be “the one”. If you’re just passing the time with someone you might as well do that locally. One man's opinion!:)