This is a tricky one. If I recall it's in 1Co6 that Paul says we should stay with our spouse. It's easy to argue for exceptions but Paul didn't offer exceptions or get-outs, the instruction was very simply to stay.
We might argue that some instructions are cultural rather than eternal but opening that door leads to all sorts of other questions. If we're throwing away this instruction because it's inconvenient, where do we stop? Can we get rid of other instructions like "flee sexual immorality"? What about the inconvenient bits about love and forgiveness? What about the bits about keeping order in church services?
I'm not sure it's inherently unreasonable to argue that some instructions related to the culture of the time rather than necessarily being eternally relevant but unless we can present an objective way to determine what is cultural and what is eternal we open the door to anyone who wants to throw away anything they dislike with little more than a bit of hand waving and "you know, culture".
