You can’t get to a good dissertation writing without getting feedback on continuous basis. It is recommended to start getting feedback early from the start of the dissertation process. Not doing so will make it difficult for the person who has to provide feedback as it the dissertation will be so lengthy so it can take week to provide feedback. Consequently, it will be difficult for the researcher to make changes on the provided feedback on the large scale.
A very important point in getting feedback is to take feedback positively and with open-mind. Quite a few people tend to make it an ego problem and perceive it to be a personal attack by the person who provided feedback.