I find 99 percent of what
@vetteguy53081 says to be correct. Second - My interpretation is that you dose prazipro, as directed, then wait 3 days, then another 3 days for it to de-activate, then on day 4(7) do a water change - then repeat - so it results in about a dose every 7 days. Perhaps I'm misconstruing it. (I.e. the dose is in the water for 3 days. You wait 3 days and on day 4(7 ) one does a water change. Note - I agree with others who have suggested that the directions are somewhat unclear - however the protocol recommended here is clear - on what we recommend.
As to the fish medic title - no one is correct all of the time. However, On this forum - its not a 'debate' between people, instead its this is the protocol we recommend. Whether Humblefish or you or anyone else recommends another protocol (or the directions on the bottle are unclear) - this is the protocol we recommend - and will continue to recommend - so - though you have 16 years of fish-keeping experience, which is great - its not going to be enough to change the protocol - and IMHO - no offense - not appropriate to come and debate the protocols recommended here - without clear references.
BTW - after carefully reading the directions - it seems to suggest that in times of severe illness, etc - you can repeat a dose sooner than 5-7 days. However - this is a routine quarantine protocol - as compared to for severe disease.
Its always good to discuss these things - and appreciate you pointing out (as well as some others) - the poor clarity of the directions on the bottle!