Post separation Adultery is illegal in NC until absolute divorce, as I understand it. Does a properly written Separation Agreement shield me from subsequent attack for post-separation adultery prior to the absolute divorce? Language similar to “…parties may conduct themselves as if never having been married…” etc. ? What restrictions would there be on cohabitation, or would there be any restrictions to worry about other than continuance of alimony payments?
Adultery is still a crime in NC and therefore must be prosecuted by the state (which hasn’t happened in a great many years); your ex does not have an action for adultery.
If you have a Separation Agreement it likely states that you are each free to live as if you are unmarried, similar to the language you have quoted you should be in the clear. The language regarding restrictions on cohabitation relates only to alimony. If a spouse who is receiving alimony begins cohabitating with a member of the opposite sex alimony ends.
“…your ex does not have an action for adultery…”
Please explain this in layman’s terms. What precisely do you mean? Do you mean it is the State who would prosecute for adultery, should that occur (which hasn’t happened in years), and that my Ex would not be the plaintiff in such an action. Does that effectively mean that the only issue is whether “cohabitation” has occurred which would be cause for cessation of my alimony? Thank you for explaining that phrase for us Laymen and Laywomen 
No civil claim lies for adultery. Meaning your ex cannot sue you personally for adultery, post separation or pre-separation. Your ex simply cannot sue you for adultery; such a claim does not exist under the laws of North Carolina.
The only restrictions with regard to residency are that the person (if any) receiving alimony looses their rights to receive if they begin cohabitating with a non relative member of the opposite sex.
However, if it has that standard language in the agreement, it doesn’t apply to 3rd parties. Which means that your spouse may sue the partner for AA or CC unless a 3rd party waiver of claims is put into your separation agreement.
(Note: While AA isn’t valid if you got involved after separation, presence of such a relationship after separation MAY be used to corroborate any preseparation claims. For instance, if you have a relationship after the separation, the wife can come back and claim that your partner committed AA if you worked together or knew each other prior to the separation. Yes, it would be impossible to prove and cost a lot of money, however, that doesn’t mean that they won’t attempt it out of sheer spite. I’ve been dealing with this myself for a while now.)