longevity and oil line on secondaries is second to primaries. secondary stiffness is weaker than primaries. If you bow is not tuned well or for some reason or not you are getting some shelf slap, your secondaries will show more sign of wear quicker than primaries.
Birds prune for several reason but one of the main reasons is to re-oil their feathers. primaries are thicker therefore they contain more oil than secondary.. one bonus of using smaller height primaries is that you can cut your feather totally out of the oil line..When feather gets wet, you can pop shaft several times against legs and most water will shake off for a usable shaft immediately. secondaries will just lay there down on the shaft.
But yes secondaries make usuable feathers but lack the physical properties of the primary.