They won't short of an admission by the immigrant of outright fraud, imo. We sometimes forget that both spouses submit a LOT of evidence to attest to the authenticity of a marriage. Sometimes, it's better to divorce, move on, and seek happiness for yourself. Sometimes, it is to the advantage of the US citizen for the immigrant to obtain citizenship as soon as possible. That is the fastest way to terminate the obligations of an I-864.
Note: There is no 10 year limit if the immigrant never accrues 40 work credit quarters.