Relays typically are very dependable - last forever. Basically check the voltage to the coil and/or the car voltage. If it is 12-14 volts, then the relay should work forever. If the voltage is say 20 volts, then that could burn out the relay coil.

Like a light bulb which has too much power applied - it will burn out.

Anyway other than that, I have been buying a LOT of crap lately (stuff for around the home). Does not work out of the box, not designed exactly right, or stops working within a month. This stuff is made in China.