It is always recommended that you have signed agreement at the end of a mediation, even if the agreement is only a term sheet, subject to later incorporation of a formal agreement. Having a signed document should prevent parties from having buyer’s remorse the following day. You may even want to consider having language in the term sheet that explicitly states that this is a binding agreement.
In a recent New Jersey Appellate court decision arising out of a nasty divorce (husband in his eighties, wife in her seventies!), the parties reached an agreement after a long mediation, only to have the wife attempt to back out. The court upheld the settlement, and an important consideration was this handwritten statement in the mediation agreement:
[t]he undersigned agree that they intend to meet with their attorneys and have a property/martial settlement agreement drafted consistent with the terms of this agreement. Both parties further agree that this document constitutes a binding settlement agreement.
Beim v. Sawyer, A-2816-10T1, 2012 WL 634638 (N.J. Super. Ct. App. Div. Feb. 29, 2012)