It is a good practise especially since young kids drool and perspire all over the covers when they sleep. Parents are encouraged to provide a fresh set everyday and as much as possible the centre discourages pillows and blankets. In most cases, the centre is mopped twice a day, toilets washed at least twice a day as well. Mattresses are disinfected daily. And most centres use disinfecting detergents. The frequency of cleaning is definitely much higher than in most homes. But that has to be the case given that traffic is much higher as well. In such cases, understand that the centre is trying to maintain a certain level of hygiene for the sake of the children. Life will be a lot easier for the staff if they allow the covers to be used for an entire week and they don’t even bother to remove the covers from the mattresses at the end of each day. If you really are unable to provide a fresh set everyday, at least bring it out to air and maybe spray some disinfectant on it before packing it into the bags again.