Until I was finally able to find a place to buy the filters I was using the same one for a month or more. I'd actually wash it off when it got too dark. It wasn't that I'm cheap, it's that I wasn't as knowledgeable about pipes in general when I bought it. And the fact that I bought it at an antique store I assumed they were no longer being made. I asked the guy at The Tinder Box about filters for the pipe and he said, "I haven't seen a Carey Pipe for years". And since the pipe I bought from the antique store was still in the original box dated sometime in the 70s' - and it appeared unsmoked - and had a few extra filters in the box, I used them sparingly thinking it was a discontinued product. Then one day I was on EBAY and discovered a place where I could buy an entire tube full of Carey filters for dirt cheap. I also discovered that the Carey Pipe Company was still in business and making pipes. So now I change filters after about five smokes.
The Carey Pipe is a great smoker - but @motie2 will probably concur, that they can be a tricky pipe to light. Since it draws air from the outside like fish gills if your pipe is packed too tightly, you can still get a draw when puffing on the pipe. But the air you're pulling is isn't from the draw-hole of the pipe ... but the gilled filter system. You can draw you're ass off but you still won't get the pipe to light. So I always put a pipe cleaner through the pipe all the way to the bowl before packing the bowl to make sure there is no obstruction. That way when I pull out the pipe cleaner I'm sure there is nothing blocking it. And when I draw on the pipe to light it - everything is right with the world. And a Carey Pipe is a great cool smoking pipe. Even some of the cheaper aromatics that have a tendency to give you tongue burn smoke a lot cooler in the Carey Pipe because of the filter design.