I think I know the answer- but I do have to pay these forever, as long as I am working, yes? (And earning more than £x per week.)
Reason for asking is that I have enough contributions now for a full state pension (have had a prediction) which I will get in a few years from now. If I carry on working and receive a state pension (I have an occupational one too which I get now) will I still pay Class 2?