I'm one of those people that always forgets when to replace something. Having mental conversations that go something along the lines of "how long have I had these contacts in exactly?" or "when did I buy this mascara again? I mean, it doesn't seem that old..." are incredibly common with me, so these bamboo toothbrushes spoke to me. Never again would I have to wonder when I needed to replace my toothbrush.* (And bonus points for actually being attractive toothbrushes!)
Now if only I didn't use an electric toothbrush...
*you know, in case that question plaques you.