I've been wanting to attempt car fresheners myself, but I didn't like the ornies. I love the idea, but so far not a single scent I have made, other than one that included cinnamon, lasted longer than a day. I never had one melt though, so I guess that's a plus and it was up to 115 inside my car one day (it did warp the poor ornie..) but at least nothing melted apart. The cardboard fresheners look like they are a lot more work for less profit, or that's how it seems to me. Most likely not, but that's how I see it looking at them right now.