The benefit of past dissertations is great and obvious. There are two aspects about past dissertations that can be considered. The first one is the benefit of past dissertations for those people who do not have a clue how a dissertation should be written and organized. Such people can benefit greatly from studying past dissertations, since they are the best examples. But I would like to dwell upon the past dissertations that you have already written.
 
The silliest thing you can do with your past dissertations is just throw them away. It means you throw away all your efforts and time that you devoted to that dissertation. Did you forget what a hard work it was? Better think of something else that you can do with your past dissertations.

• The main thing you can do with your past dissertation is to publish it. Publishing is rather expensive, but if you dream about a serious academic career and general recognition, you will have to spend money to publish your past dissertation.

• Past dissertations will be extremely helpful if you feel like carrying out deeper research on the problem. If you were not too smart and turned your past dissertation into heaps of useless trash, you will have to start the whole research all over again. What is more, you will do double work, because you will need to look for the same materials. But if you have your past dissertation, you will just continue your research.
• Past dissertations are a good occasion for a strong pride. First of all, you can be proud and respect yourself. And when you get older and have your own children, you can tell them a story about the main work of your life. Your children will definitely be proud of you. Moreover, it can be a good example for them to follow.

So, do not hurry up and think twice before you get rid of your past dissertations.