You're suppose to replace the original nitrophly floats because modern fuels can cause them to get heavy and lose their buoancy. I have four carburetors to rebuild, so that leaves one spare. The brass floats ought to last forever.
I did test the nitrophly float from the carburetor I'm rebuilding. It hadn't lost its buoancy so I may reuse it. It's pretty simple to replace the float it there are problems in the future.