I'm guessing you are claiming damage due to USPS handling? If so, the PO will nearly always claim insufficient packaging as the reason for the damage and therefore deny the claim. The only way you could possibly win such a claim is to have a package that had a tire track across it and you could prove that the tire track was that of a USPS vehicle. Even then, the PO might deny on insufficient packaging grounds.
As a practical matter, the only time USPS insurance is good is if the package is completely lost, i.e. there is never a delivery scan.
Finally, USPS insurance, if bought separately costs about 2% of the insured amount. My experience, having shipped nearly 5,000 packages, was zero losses. I did suffer one loss on an inbound package though. At my loss rate, 2% is incredibly expensive. Better to go to the cookie jar insurance method where you set aside a small amount from each sale to cover losses. On my experience, 1/10th of one percent would be quite adequate.
