they just exist, and so do their wives back home. The marriages from the subcontinent are arranged marriages usually; spouses don't know each other very well, so if one of them takes off for two years at a time...it's kind of like back to normal for them.

Long distance relationships don't usually work well if they're filled with prolonged absences. Two years until you see someone again? And you expect that your partner would remain faithful to you? I doubt it. Maybe if both agree to have an "open" relationship, it could stand the test of time, but then do you really want a relationship like that? Most wouldn't.

Short absences (husband is a pilot, or works offshore; wife goes back to school for a semester, etc.) I think can be managed, but longer than a few months and I think even the best-intentioned individuals would be tempted to stray.