Yes too many baths is a thing, just like a human taking too many showers, it can dry out their skin. It's best to only offer the dust bath about 2-3 times a week for long enough for the chin to bathe (normally about 5-10 minutes but some like to bathe longer). Depending on your climate and how much you handle the chin though you may need to do more or less baths. If they look or feel greasy then increase the number of bath days, if their skin on the feet and ears looks dried out and flaky and/or the chin is scratching a lot decrease the number.