Being separate from each other for a short or long time does not nullify the marriage. In the rulings related to marriage, a husband is not allowed to travel or be away from his wife for more than 4 months. In the case that he does, and the wife does not approve of it, he is sinning and if she does not approve, it will be grounds for divorce.
So, if the husband abandons for more than 4 months, he is committing a sin and that is haram, unless the wife approves, or he has a valid excuse, or the husband had stipulated this in the marriage contract.
But, in any case, the Nikah will still be valid, and it will not automatically become nullified, even if years pass.
However, if the wife give consent, and approve of being distant from each other, then that is permissible and allowed.
And Allah knows best.