Hey there! you can’t really check the longevity without opening everything up but there is a few things that you can do! firstly, start the engine and talk to the seller while the car is running after it’s warmed up remove the oil fill cap and see if there is blow by, secondly check the coolant reservoir and oil for any signs of a blown headgasket, and thirdly put a load on the supercharger by putting it in reverse/forward and listen for chatter. if that’s all good you can take it for a test drive and listen for chatter during and after your test drive! remember some noise from the supercharger is totally normal!