3 years is the accepted norm. I believe the original idea was to have rows of 1st, 2nd and 3rd year plants, so the bed in a large patch precessed across.
However, you may find that by the 3rd year row weeds are a problem, so it needs to be removed and dug over.
We are currently solving our weed problem and Strawberry beds by a method seen elsewhere.
1. Select runners and place in small 3'' pots with compost around August.
2. Dig over row/s and try to get as much perennial weed root out as possible and add compost.
3. Cover the area with black weed proof material and retain cover with plastic retainers.
4. Cut out planting holes, by X's and turn back the material to give a reasonable space for plant and watering/feeding.
5. When the runners have settled into their pots and have some roots showing at the bottom of the pot, cut off and transplant runners into the holes watering well.
We have completed our second bed on the strength of the yield of the last years trial. It was easier to pick, feed and water. Next year the third row will be started.