imo, no single feeder should make up more than 40% of the overall diet regardless of what it is. that being said, bsfl, aka pheonix worms, calci worms, are one of the best single feeders you can give your cham.
a good balance of protein to fat, and one of the few feeders that actually have a favorable ca/p ratio. they also have lauric acid an enzyme that is said to discourage coccidia and other pathogens

.
diversity is key, however that also needs to be weighed against nutritional balance of other feeders to be offered. im not so sure that diversity is that important if it means replacing a balanced feeder like bsfl with less desirable feeders.
so, imo, feed all of the cultured bsfl you want (as long as it doesnt exceed 40% of the overall diet). probably preferable to what you would offer in its place anyway.
bsfl pulled directly off of a compost pile, now thats a different story, however bsfl can be washed.
bsfl have a tough rubbery leathery skin that many chams find hard to digest, so i always recommend offering some other feeder in between bsfl feedings and also taking the occassional bsfl break.
a common practice is to nip them in the sides with a fingernail clipper, so the chams digestive juices have a place to get a hold of. if you start getting large % of mostly undigested bsfl, probably good to slow down or give it a rest for a while.

jmo
ps this might be a little less confusing/easier to read, than the joshs frogs site.
http://www.beautifuldragons.com/Nutritionframeset.html