Does a separation agreement expire?

In New York, typically, separation agreements do not expire.  They can be revoked or modified by mutual agreement of the parties.  In a few cases, a separation agreement, or parts thereof can be set aside by a court.  Reasons to void parts of the agreement or the entire agreement might include, but not be limited to, if it is:   void against public policy; obtained by fraud, duress or one party was mentally incapacitated when making the agreement.  Matters involving custody and parenting time of children, as agreed to in a separation agreement, should always be reviewed by the court to make sure it is in the childrens' best interests before becoming a part of a divorce judgment.  Custody and parenting time agreements can also be modified if there is a substantial change of circumstances and a court determines that it is in the best interests of the children to modify.  Give me a call if you want to discuss your situation.  It would be my pleasure to speak with you about it.  

A separation agreement is a contract between spouses that determines the same issues that would be addressed if they were getting a divorce (e.g. custody, visitation, child support, spousal maintenance, division of property, etc). The agreement is binding on both parties can be enforced through the courts.  As to your question, a separation agreement can be for a set length of time if the parties specify. However, a separation agreement is typically without an expiration date (and is eventually merge into a divorce decree).