In my humble opinion, most doms make the same mistakes. You don't take enough time to get to know each other beforehand, it's straight down to business. During this time, the pace picks up far too quickly, and after a few days you already have a hundred thousand rules to follow. It often fails because even an online relationship takes time and it is an intrusion into ones previous life.
Time difference is also a big factor with more than 1 to 2 hours difference I personally haven't had any good experiences.
And last but not least, how well do the kinks fit together? If my Dom has a certain preference that I don't share, it won't last forever. Either it fits or it doesn't.
Of course, trust and communication are also important. For my part, I want to talk to my dom regularly and I don't necessarily have to play, on the contrary, I like to just talk and exchange thoughts.