Is it really worth it!!!

I grow a few veg in my garden and this year decided as well as growing spuds in the ground I would grow some in bags so I can compare. I grew Charlotte and International Kidney. I've just emptied my bag of I K and what a pathetic crop. Not even 1lb in weight. I did have rather a lit of minute ones so I am guessing I have emptied the bag too early. Could that be th e reason?
I have decided to leave the bag of Charlotte for a while longer but all the leaf is dead. Will they still carry on growing if I cut it all back?
Thanks

I dont like growing corn, I don't think its worth the room, the time it takes and the yield, so I dont grow it, shop bought from the grocers is always cheap and to me tastes the same, but then again I like the stuff in the tin as well