We wish there was a stock-standard answer to this question, but truth be told, everyone is different. On average, most people's flow is heaviest on days 2 & 3, so they tend to need either heavy absorption pairs or more pairs on these days. Some of our customers can manage with 3 pairs for their entire cycle by washing straight after wearing (especially the quicker drying nylon fabric ones) whilst other customers have to change every 4 hours because their flow is super heavy. We always suggest that you try your blushproofs at home, in a safe space first, to work out what is best for you and how often you should change. So, back to the question - you probably need at least 3 pairs...