FAR 23 simply states that there must not be an unrecoverable spin and my copy of AC 23-8 is quite clear that recovery must not take too long for it to be deemed not unrecoverable:
(3) Abnormal Control Usage. ...
Abnormal control usage should be evaluated at several points throughout the spin to ensure that uncontrollable spins do not occur....
Following abused control usage, reversion to normal pro-spin controls for up to two turns is acceptable, prior to the normal recovery control inputs, which must result in recovery in not more than two turns. In addition, going directly from the control abuse condition to the normal recovery control condition should not render the spin unrecoverable. For example, after evaluating the effect of relaxing the back stick input during the spin, it would be reasonable to expect the pilot to apply normal recovery use of rudder and elevator without first returning to full back stick.