Quick Answer
AAMC PREview scores are valid for multiple years, and AMCAS automatically releases non-voided PREview scores from 2020 onward to AMCAS applications.
However, that does not mean applicants should assume every older score will satisfy every school in the same way. A school that requires PREview may not consider an application complete until a score has been received. A school that recommends PREview may allow applicants to submit with or without a score. A school that requires a situational judgment test may accept PREview to satisfy that SJT requirement. Other schools may be exploring PREview for future use without using scores to evaluate applicants in the current cycle.
Because those categories affect timing, an applicant with an older PREview score should still check each school before deciding not to test again.