Subaru Crank Sensor

Hi guys. I had a problem with my 95 subaru impreza when I bought it a few years back. I would drive it to the store, come out and it wouldnt start for about 5 minutes. It got so bad, that it started dying at lights. Well I bought a $26 crank sensor as suggested by subaru and never had the problem again. Here I am two years later and its doing the same thing. Do these sensors usually go back this quickly? I heard its a common thing but didnt realize I would have to buy one every few years. Thank god its cheap!