The longest diapers can go without washing is one week (I learned this working for a diaper service, which only picks up once a week). After one week they will start to attract bugs and start to grow (it's true... missed pick-ups required special attention to get them back to proper hygiene standards). If you plan on letting your diapers sit longer than 3 days, I would highly recommend spraying each poop diaper with BacOut enzyme spray (after removing any solid food poop) before you put it in the pail. The spray will prevent the growth of bacteria, hence help prevent odor and staining.
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For your current stains, sunning will work wonders in just a matter of hours. If you lay them out on towels (as opposed to a clothesline) just turn them over in about an hour so the other side gets sunned as well. If you have any particularly stubborn stains, sprinkle with lemon juice and lay them out in the sun, then rewash. Works like a charm AND kills fungus and bacteria.
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But to specifically answer your question, yes, you can use bleach on prefolds without issue and you can use it occasionally on your premium diapers as well. I would never recommend weekly bleaching of premium diapers, but you can do it on occasion when it is necessary- like they are infected with a nasty virus like rotavirus. Bleach can irritate baby's skin, so I recommend extra rinses after a bleach wash. An alternative to bleach in the wash would be oxyclean. BioKleen (also the makers of BacOut) makes an environmentally friendly oxygen bleach.