A risk based approach that makes sense for your operation. You aren't dealing with raw, exposed product but you are dealing with packaged food that is destined for shipment. What if a customer were to purchase that product so they could unpackage it and "rework" it into another final product? I recently blogged on this very subject. My personal opinion is that the act of registering every small piece of glass and then walking around with my clipboard is a waste of time. Controlling your program through establishing a robust plan (SOP), educating your staff, following through with breakage and personnel inspection procedures, etc. are were you gain true success. If my breakage procedure is severely lacking, I am setting myself up for failure and my risk goes up, thus increasing the frequency of the audit. Vice versa, if my control is such that the risk itself has been reduced, I can reduce the frequency of my audits (based on the verified level of control).
Funny story: during one audit, I was walking through the warehouse discussing the very matter of a glass recall that another manufacturer was having when the auditor and I both stopped after hearing glass crunch under our feet. An unprotected light had fallen to the floor below. The warehouse supervisor swore it had to be within minutes, because he had double checked the warehouse before we got there. Murphy's law in action!!