If spouse acts in a new, changed way when it looks like a relationship may be finishing, is the change likely long term?

E. g if the relationship had been dead for a long time, if they found out you were talking to someone new etc, then decided to change behaviour to how you always wanted them to be to try to save the relationship. How likely is this to be sustained behaviour?

If spouse acts in a new, changed way when it looks like a relationship may be finishing, is the change likely long term?
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