I may be completely off on this but I believe that health insurance is one of those things that should continue during separation if you currently carry your spouse. Or at least continue for long enough so that the spouse has a chance to get their own insurance…They may also be able to be removed during annual enrollment…
I know that my husband did drop his ex from his insurance but he gave her warning of when he would be dropping her, though they did have a separation agreement.
I think that the most common practice is that a separation agreement would protect you from future liability on claims because normally, equitable distribution and all is covered in the agreement. There is also normally a statement such as “Each party, from X date agrees to live separate and apart from one another as if they were not married”. This may make a difference on an insurance claim.
My suggestion to you would be, check out the sample separation agreement and modify it to suit your needs, consult an attorney to get one drawn up. A separation agreement protects you both and can settle a lot of issues that may normally end up in court.