Occasionally it may happen that couples who were determined to separate will reconcile. It usually depends how far down the line of divorce they have gone. Many couples would consider reconciliation more readily if some of their issues could be addressed on a contractual basis before actually reconciling.
Such agreements may deal with property or money issues for the most part. They are worth doing as they serve to focus the couple on some of these issues may have been part of what brought the couple down the road of separation in the first place.
What weight a court would place on such an agreement remains to be tested but the agreements would serve as a benchmark for a judge perhaps as to the intentions of the parties should they eventually separate or divorce.