Strawberry confusion

Strawberries are the oddity in the plant world. You put in new plants, and if in early enough, you should get a crop that year. To propogate itself, the plant throws out 'runners', young plants by means of a sort of surface branch (runner) which will root the baby plant on its end. Mom plant, meanwhile, has exhausted herself somewhat and needs a good haircut and feeding after finishing fruiting. The idea of the runners are simply to find fresh new feeding ground, which will always be away from the mother plant. The mom plant, with regular haircuts (cutting off all old leaves) and feeding will remain viable for a few more years but will gradually degenerate to a point where it's just wasting space. The new runner plants will take over but eventually reach the same worn out stage.
In essence, the initial plant you bought won't live particularly long. Some people don't allow the runners to form, thinking it starves the mother plant, but it's not what nature intended. If you follow this method, you'll need to totally replace your plants every few years to keep up production.

I've had many runners and some mom plants for quite some time now, but I do trim the moms after fruiting and feed them all.  Call me cheap, but I do get respectable yields from my runners when they mature the following year.