Talking to a room regular as I write this. she's getting collared on Monday, to a Man who's 7 (or 8, depending on the time of year) time zones ahead of her.
It wreaks havoc on all but the strongest on-line relationships. As I wrote last night, the simple act of being here for someone . . . is what creates the strong, long-lasting bonds between Master/Mistress and slave. In the absence of it, most on-line relationships, partticularly in D/s, suffer, and ultiamtely fail -- either directly because of the time zones issue or as a result of other issues that fester and mount, exacerbated by the time difference.
In the particular case of the girl I'm talking to right now . . . I think, as well as hope, that the relationship will be successful. she has the maturity and the inner strength (when she allows herself to relaize that she has that strength) to hande the ups and downs of a very long-distance relationship. she has been in this big time difference situation before -- it didn't work out well, but that was mainly because the Man in question simply couldn't be here enough for her. This situation, so far at least . . . looks to be different.
But in general, My advice is to look for a Master/Mistress/slave close to home, time-zone wise. It removes one potnetially huge obstacle. And truthfully, there are so many to begin with that no one needs any additional ones.