A few things to consider:
The plants should be most productive in years 2 and 3 - ideally they shouldn't be allowed to produce either fruit or runners in their first year (OK, perhaps just a few strawbs then!
)
They should be replaced in year 4, so to maximise production the replacements should be 1 year old plants, which means allowing a few runners to develop from your original plants in year 2.
Best to use new soil/compost to avoid the build up of disease.
I'm sure there are many different versions of this outline plan depending on the facilities you have and also whether you can remember which year you did what!