I view the formal interval as twenty eight days from the initial poke. Quite a few individuals alter or overlook this rule though. For my part I feel everyone ought to study the matter personally prior to settling on their own ease rather than just imitating decisions made by others.
I cracked open a fresh bottle of that sterile mixing liquid not long ago and now I keep wondering how many weeks it remains okay to use. With my ten-piece set I figure on going through the portions singly. My aim is to stretch every drop of those thirty milliliters by handling things this way.