Hi J.,
I looked into sterilizing bottles when my first was born. I have 3 now, with 1 on the way. I spoke with my ped about it, and I was told that in this day in age, you really don't need to sterilize like they did back in the day. With the anti-bacterial soaps out, sterilizing is not that important. However, if you have a daycare setting, where there are multiple children from multiple homes around your children, then you probably should sterilize periodically. I have rarely sterilized my children's bottles. Now, one day my daughter took off her diaper in the crib, which was a dirty diaper, and got poo everywhere (she had a bottle of water in there), I definately sterilized in that case. Also, my son did something similar with his sippy cup, so again, I sterilized. Really, you only need to sterilize during extreme cases where their cups/bottles come into contact with something that soap may not really disinfect. If you clean the bottles/cups daily, sterilizing is not important.
Good luck & God bless!