You don't HAVE to Ned. Monty Don experimented with this a couple of years ago. The result he got (if my aging memory serves me correctly) is that the earlies did provide a better crop when chitted but for main crop it did not make much difference. Of course, with my memory it was probably the other way round.

As S says, you don't have to. We usually receive our seed potatoes several weeks before I am prepared to plant them. I don't like to keep them in contact with each other in their bags so put them in individual modules ie I chit them anyway.

I stick mine in egg boxes as I still like 3 on mine before planting as I think it gives them a good start.