Your dealer is probably right about the break-in. You can speed up this process with the Cardas Sweep and Burn-In record, but follow the instructions (check out their web site).
Hum a problem with Planar 25/ Grado cartridge?
Disappointed with Planar 25/Elys combination. Dealer said cartridge needs break-in period of a couple of weeks. Have always preferred Grados but understand there to be a hum problem with this combination and not with the Rega cartridges. Ideas about Rega carts vs Grado and the hum?