Got this from a book on punting years ago:

FIVE YEAR OLD SYSTEM:

Races 1600m and beyond.
When a top 5 year old who was well up in the weights on going out for a
spell, resumes again, providing it is starting over its "true" distance,
start backing it from and including its third start back. Follow it up to
three times. It often churns out good divvies, especially during Spring and
Autumn.