Hi it’s Will I think it depends on what you are trying to achieve. I have used them where the blades are an inch wide from wear along the bottom edge and they have worked fine although I think if you are in hard ground you are likely to have them snap off. I would look to see they are still overlapping otherwise they will leave undug strips. The inside facing blades that are close to the drive housing need to be intact otherwise again it will miss the middle strip. I worked on a couple of ex council machines that had cement all round the rotors apparently they used to chuck cement dust onto sharp sand when paving large areas and use the rotavator to in situ mix the sand and cement.
Best wishes William