“I tell you that anyone who divorces his wife, except for sexual immorality, and marries another woman commits adultery.”
-Matthew 19:9, NIV
I do not see a time limit set on these words.
The exemption is there for anyone who has a spouse that engaged in sexually unfaithful behavior. That is what I see in Jesus’ own words here in the Gospel of Matthew.
A faithful spouse choosing to divorce a cheater is not the problem. The problem is the sexual infidelity in the first place. Choosing to divorce a cheater is not a shameful choice.
I believe God grants humans the option to divorce a cheater out of His great mercy to faithful spouses.
He does not insist on faithful spouses remain in an abusive relationship with a cheater. God understands sexual infidelity is such an incredible breech of the relationship that sometimes ending the marriage is the best of the bad options available. It is merciful.
So, whether you decide the next day or years later, the shame is not upon you–faithful spouse–for choosing to embrace this mercy God grants you. The shame is upon the cheater for putting you in a place where you needed it.