Catalytic Converter Gaskets

I just replaced my cat with one off of a salvage car. I just went ahead and installed it since I had to get it on there to use the car, but I wanted to see if anyone could tell me what the result might be from using the old gaskets? What would I see or notice? So far, everything looks and acts fine. Fuel mileage fine. Best thing is my check engine light is off and all codes are clear again. It is so easy to take off and put back on, I don't mind if I have to take it back off to put new gaskets on. The old ones looked fine though. No tears or anything. The gasket material looked just high heat corded rope like a wood stove door gasket.

 

Good news. I hope this works out. There really is not a lot of pressure on the cat in the first place. It is held in place by two spring mounted bolts on each side. So I am assuming they do not need a lot of pressure in the first place. The gaskets were well formed though when I inspected them. But so far, no noise, and no exhaust smell. I even work at a place where I have access to confined space gas meters. Nothing in the car at all.