Thank you for all of the responses!

In your experiences, how many seeds does it usually take to find a 'suitable' keeper? Taking Blueberry for example, do you think that I should be able to find at least one out of a feminized 5-pack that is covered in crystals and tastes like blueberries, or should I expect to buy several more packs just to find a keeper?

In other words, just how much do the phenotypes vary in feminized seeds?