R.R.
I know exactly what you are saying my son (8 months old)is a nuk baby and has been sick for quiet sometime so i try to keep the nuks clean. I usually wash them every evening with warm soapy water but i also boil them when i boil the bottles. When the water seems collect inside I tend just to through them out. I probably throw them away after about a month! Hope I helped.
R. - Mom of 11 yo, 6yo, & 8 mo