Rationale - Water Validation

I am trying to think of a rationale that would say 30 Days of Chemical and Biological Testing is enough. The in-feed water supply is a validated DI water system loop. Any inputs?

Dear N3FOL,

In statistic, 30 samples data are enough number which can easily predict the trend, thats gives the reproducibilty of the system thats why in first phase of water validation 30 days monitoring must be initiated.

regards,

Thanks for your input, Shahnawaz.