I had been doing them all about 3 times a week for several months but have slacked off as of late. They have about 6-8 bones (have no idea what kind, shank maybe) laying around that are constantly chewed on. Well, except for Keiko she gets them when they are new but after a few hours she's done.
But her and Gunther's teeth are pretty good, although her gums aren't great. Nigel's are also okay, but Posey's teeth are the ones I have to keep an eye on and do scrape the tartar off with my finger. I want to get a scaler as all 4 allow me to pick at their teeth.