Sampling Question

I was just wondering during a process validation (let’s say packaging). How many samples is enough and how do justify this amount? For example, the article on packaging validation stated 2 samples are pulled every 5 minutes during the three hour run.

I always thought the amount of samples depended on the size of the batch or the size of the job. I would use ASNI/ASQC Z-1.4 standard to determine the amount of samples I need to take and it would also dictate how many defects would be acceptable.

Please any insight to help in this matter would be greatly appreciated.