Having a short, temporary separation is not nullifying the covenant, IMO.
Paul gave the Corinthians commandments that he received from the Lord in I Corinthians 7, let not the wife depart from her husband, but if she depart, let her remain unmarried or be reconciled to her husband. And let not the husband put away his wife.
It's translated put away. It could also be send away. Do believe this applies to the issue of separation as well as divorce. If a woman separates from her husband moves out, she's departing from her husband.
I don't think it applies to fishermen or businessmen going off to earn a living and coming home after the journey is over or the wife taking a trip to visit her mom in the next two for a few days. I think it refers to the 'marital disruption' type of things.
I've read too many stories of husbands who want move out for a while or a wife who's stressed and wants to live alone for a while which turn into divorce to think it's a safe course of action. I do understand why some counselors recommend it if there is violence, but I think it's like playing with dynamite, especially in our society where people readily accept divorce and there are even church leaders who seem to think little or nothing of it.