whats wrong with that ??

I believe you can lift runner bean roots and store them over the winter like dahlia tubers to start in a greenhouse and grow again the next year.

However I don't know if there is any advantage in doing this!
Gillie

I did actually try that last year but unfortunately chose the wrong winter to try and store them in the shed and they didn't quite make it through. 

One obvious advantage is that you know the plants will be exactly the same variety as the previous year, although some may not actually see that as an advantage. 

Might try again this year keeping just a few of the best roots just to see what does happen!