In 1964 I bought a compressor, had one ever since
1985 for me - a McMillan with cast iron V-twin pump, and it's still going strong!
On a very knowledgeable mate's advice, the first oil change saw it filled with 'Amsoil Synthetic Compressor Fluid', and that had scarcely discoloured when I changed it after 10 years' use! Really does seem to drop the wear rate dramatically.