How long does achilles tendon rupture pain usually last?

Several days: Usually as the swelling subsides the pain will subside with it after the repair, the pain will diminish as the tendon has been repaired and usually the pain will subside significantly over the first post op week.

Depends: It depends if you let it heal by just immobilization or if you have surgery. Surgery will usually speed up the healing process because the tendon is repaired, but this will still take about 8 weeks.