How often should you change your car battery and does changing car battery depend on CCA?

i just did an oil change in a honda dealer. my car is hond civic lx 2004. then they told me that my car battery was about 303 CCA and its supposed to be around 400 CCA. so its highly recommended to change it. 1. does changing the car battery depend on CCA? 2. how often should you change the car battery? 3. what... show more i just did an oil change in a honda dealer. my car is hond civic lx 2004. then they told me that my car battery was about 303 CCA and its supposed to be around 400 CCA. so its highly recommended to change it.
1. does changing the car battery depend on CCA?
2. how often should you change the car battery?
3. what will happen if i dont change it?
4. i bought the 5w-30 oil in walmart. they just used like one and a half bottle. i am so confused because the last time i did it, they used like 3 bottles. can that really happen??

sorry if my questions are really stupid. i dont really know much about cars, so..
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