Crop Rotation/Or not - Beans

Danny my runners have been in the same place for 12 years, I fill the planting trench with dalek compost and give them a sprinkle of BFB. 
They seem to do well, 
I sometimes overwinter a few plants in pots in the GH keeping them in dry-ish compost they soon throw out shoots in early spring.

Cheers Bren