Hi M.,
Well I am a mother of 4 and a home child care provider, so when the kids I watch now were babies and my youngest was a baby I sterilized the bottles the 1st initial time and then once a month after that. I would just wash them in hot soapy water.
Now that they are all 1 1/2 yrs old and they are all on sippy cups, I still do those once a month. And wash them by hand with hot soapy water. By the way for future reference, if you have a bottle or sippy cup that is clean but has an odor to it, you can pour baking soda in there and then put some water in there and let it soak for a few hours. Then wash like normal and go on. It sometimes is caused by juice and coninually putting milk in them. Samething with formula.
I have a new baby starting Monday, and I will be sterilizing all bottles that mom brings me and pacifiers. And then once a month from here on out.
Hope this helps, W.