Bleach is corrosive. Fabrics and plastics corrode. Over time, that's gonna happen, and corrosive materials like bleach will shorten the lifespan of your diapers whenever they reach "critical mass" of all the factors it takes for the materials to react that way. Because that point occurs at an unpredictable interval, you hear a lot of, "No bleach," warnings.
Use at your discretion. Definitely I use it from time to time. It's contributed to some cracked PUL for sure, but I also have PUL stuff in my stash that's older than the stuff that cracked. There are just too many factors to know how much bleach/how many exposures is too much.
Laura, mom to ds "Big D" (1.09), dd "Azalea" (10.10), and twin girls M and B (3.13)! Wife to my favorite. Cloth diaper industry geek. Birth geek. Church geek.