Under the guise of religion, we marry "Til death do we part". However, in reality we marry until the mood hits us to divorce our spouse. I am agnostic, bordering on atheist, and do not believe in Heaven or Hell. I believe that marriage is nothing more than a legal arrangement in which we sign a contract stating we will be there financially and legally for another person, with the "emotionally" thrown in for good measure.
In the event that the Heaven my Mom talked of so many times truly does exist, I believe her and my Dad would still be married. As none of us have ever truly been to Heaven (again, if it truly exists) none of us can testified to whether marriage ends when we leave Earth, or if it continues on for all of time.