Wool covers are best for over night.Wool is an excellent product for diaper covers since it naturally repels bacteria and odor. It is very breathable which helps prevent diaper rash when you can’t change baby as often and it keeps baby cool in summer and warm in winter.If your wool does not get poop on it they can go up to three months in between washings.Your wool covers should be hand washed with a wool wash and lanolin should be applied once in a while to help it stay water proof.When you first get your cover it may not be very soft but the more you wash it the softer it will become, then of course you can go longer in between washings.