I would have to think that there definitely IS a break-in period for an entirely new tt bearing system, of most types. This would vary according to the nature of the bearing (there are many types) and the materials used in the bearing system, including the thrust pad (ditto). What you might hear during break-in is slightly more noise than what will be the eventual norm. Most likely, the variance will be from "no noise" to "even less noise". So, forgeddaboudit.