Ross, how many chances/bloomings do you give them before they get the boot?
It depends on what good qualities the flower has. #4, for instance has only wide petals to recommend it. The colors are blah and the notch in the pouch would probably be there on subsequent bloomings, is my guess. Therefore, I won't bother reblooming this one. #5, however has much nicer color, better shape and a double flower. I will probably keep this one to rebloom. The only other one from this cross I've kept, so far is #1, which is currently in bud, again.
If I like something about a flower, I will rebloom it until it has at least three to five healthy growths. That usually makes three bloomings. On average, I'll keep 1-3 plants from a flask after seeing the blooms. Sometimes I don't keep any.
With the Paph Barbilights, I've bloomed or budded about 20, numbered and photographed 12 and plan on keeping 4 for reblooming. I also have another dozen or so yet to bloom. The unnumbered ones that were in bud and sold before blooming were done so because the growth habit of the plant was larger than I wanted.