With my six children together, I have never sterilized my bottled but a few times altogether, and this was then they were new as recommended on the packaging. It gets off the "factory germs."
Every day is a bit much. If it makes you more comfortable to do it, one a week is more than enough: I would have said once a month if you felt it was really necessary.
What sterilization does is prevental bacterial growth. Up until the 1950s, water standards were not very high, so sterilization was necessary. Now, people just happen to keep that outdated habit.
If you have water that comes from a well or cistern, the boiling your water for 10 minutes is probably recommended, as well as the sterilization of the bottles. If you have city sourced water, simply having clean bottles and nipples washed with warm, soapy water, is adequate for the health of your baby.