That was unclear in the preview. You could take it as a one night thing, but scenes also reminded me of the movie w/Alan Alda, Same Time Next Year, in which he has an affair once a year, for many years, with the same woman. I saw the families and wondered if the guys were still getting together, but when I asked my friend if they kept seeing each other, she said no.
Thanks for clearing it up. The idea still sucks, tho. No reason to see this one.