My ears are getting a little thinner. I was wondering if the effects of Botox will help that out?
Botox will not help your earlobes get bigger. You may want to consider a dermal filler such as Juvederm or Evolence. Also, you could consider fat transfer. Botox works by paralyzing the underlying muscle to reduce tension on the overlying skin. This mechanism is not present in the earlobe.
Although facial aspects/characteristics change as we age from childhood to adolescents to adulthood these changes are all usually in ratio. So although your earlobes may be thinner this may not be a bad thing as they are likely in ration to the rest of the ear and face. In addition wearing large/heavy earrings can result in elongated earlobes that will thin as they lengthen. I don't see much benefit to fillers or fat to make the lobes larger.