I never heard of a 10 year rule either. We don't need to split up the retirement benefits as they are about equal already. I looked up the IRS publications on divorce and it doesn't specifically address my question. Luckily I found the publication on home mortgage interest deductions and it has directions for what to do it you're splitting the deduction between 2 people. I've included the link as this might be helpful to others going through divorce.

IRS instructions for Divorced or Separated Individuals