It's been my experience (I'm in PA zone 6a; clay soil) that when a strawberry bed starts to "peter out" after a couple years you'll do best to dig it up and replant. I know they say not to replant the young "runner" plants because of possible disease, but I've had good success with that. Here's my humble advice: Go ahead and keep your bed watered and fed (I'd give it Miracle Gro maybe once every week or so). Mulch/feed it with compost (bagged cow manure is a good fertilizer for strawberry beds...it's easy to work it in around the plants; you can buy it at Lowe's/Home Depot, etc.) Harvest what berries you can from it.
Then, in the fall, when the weather is cool (September/Oct), prepare a new bed somewhere else and lift the young plants from your old bed and replant. Or, of course, you can dig out the bed, amend the soil with lots of compost and replant there. OR you can buy all new plants and replant.
One other thing you might try (my friend does this): once you've picked all the berries, cut the plants right down (he runs a lawnmower over his bed). Then keep them watered and fed and you should see new growth very soon. I'm a little leery of this, so I'd only do it on part of the bed first to see how it goes. Good luck.
