Spousal Health Coverage during separation

My wife and I recently separated and I want to keep her on my health plan, until she can obtain one for herself. How long am I allowed to keep my wife on my company’s health insurance plan, with or without a separation agreement? Also, if my wife and I decide to create our own separation agreement and have it notarized, is the content legally binding until we have a lawyer draw one up for us?

You may keep your spouse on your insurance for so long as you are married, in fact I have seen cases where the parties had a separation agreement, lived separate and apart, and did not get divorced for several years so that one party could remain insured.
You may create your own separation agreement, so long as it is signed by each of you before a notary it is legally binding whether or not an attorney was ever involved.