I know someone who did this. Circumstances were slightly different, but...
She lived in Australia, had 2 girls one aged 15 one aged 17, both at school still, so a particularly important time for them, particularly the 17 year old who was doing the equivalent of A levels, but also the 15 year old who was doing the bit you do before A level equivalent (different system over there)
I figure she thought it would be okay because of their ages. Basically she was offered a postgraduate something or other at Cambridge, so a pretty fantastic opportunity for her to be fair.
The main difference I suppose is that she was not able to fly back once a month but she did return several times in the year and the girls flew over etc. So its not like she buggered off and didn't come back for a year or anything.
Turns out her and her husband had an agreement where they could have sex with other people as long as it was purely physical.
Except he fell in love with the woman he started seeing.
She came back, they tried to work it out by him breaking up with her and they even renewed their wedding vows. But it was over, he couldn't stay, so they split.
She got a bit bitter and issued the girls with an ultimatum to either be loyal to him or loyal to her. One chose him, one chose her. Family completely split. (She was a bit of a nutter to be fair)
Husband is now shacked up quite happily with new wife. Girls have a tentative and long distance relationship with each other, but its all a bit stealth and secret due to the mother thwarting it.
She makes out it was all his doing but honestly I think she tempted fate by buggering off for a year. Having said that, it was an amazing opportunity for her.
That's pretty far removed from your situation but I thought I'd share anyway.