We do Finley and Gizmo's teeth every night at bedtime, with the exception of a night here and there where we're just too tired by that time lol. Yes, they are prone to bad teeth so yes, the more the better, but 4 days a week is probably sufficient. Use an enzymatic toothpaste, and the toothpaste itself will do a lot of the work for you. So even if you can't scrub her teeth as well as you'd like with the brush, the paste on her teeth do some of the work making it less essential to really brush. I have been told, but have yet to actually confirm with our vet, that it's really the outside of the teeth you need to worry about more than the insides...