I have not bred yet but my hold back will be based on 2 major things: goals for future breedings, and quality.
I dont plan on replacing any of my snakes at all, they are family. But i do plan on holding back snakes that could replace some animals.
I am going to be breeding 2013/14 season my black pastel het albino male with my albino female, i am praying i end up with 1.1 albino black pastels because i was to produce blizzards. So i would essentially i would not need a black pastel het albino if i have a albino black pastel, but i might want to use him for other things where the albino is not a major part.
I also plan on breeding my killer bee to my pastel lesser female, i am 99% sure that i will not be holding back any pastel,super pastel,bumble bee, or killer bee males from that clutch(could be a unique one). this is the reason i spent the extra money and saved for a killer bee male instead of a bumble bee male, to reduce the temptation for me to want to hold back as few males as possible from the clutch.
My overall hold back plan is to have a 1.2 or 1.3 hold back ratio, for all the breeding i plan on doing in my life.