With DS I had some Kushie Ultra AIO and the covers degraded after about 18 months. I had tweleve and used diposables at night so it wasn't as if I was washing them excessively.
I now have some new TotsBots Easyfit AIO for DD. I have been washing them in TotsBots "Potion" powder, which they recommend to be "kind" to the outers in the hope that they will last as long as DD is in nappies. But it's not cheap and I am not impressed with it's cleaning power tbh.
So, if you use AIO or pocket nappies, what do you wash them in?