I have a forty year old service station compressor with a large tank which is two stage.  The old slower turning compressors with cast cylinders will last for years.  Some of the newer stuff with aluminum cylinders turning at high speed will make air, but not forever.  Be sure at least to have cast iron sleeves.  Newer stuff tends to hyperbolize hp ratings, but check the amperage and do the math and you will get a better idea of the machines capabilities.  A 6.5 hp &amp;quot;rating&amp;quot; doesn&#039;t mean you have a six-and-a-half hp motor pulling your compressor!!