I gave up with NCB protection years ago. It adds a reasonable amount to your premium. If you haven't made a claim for many years it implies you're a fairly good driver and probably won't make one in the near future and, if you do, your NCD only goes back 2 years ie, to 40% instead of 60%. All in all I worked out that if I didn't make a claim for about 4 years (I think) I'd be quids in and it worked.
Get a quote with and without NCD protection and do your own sums.