I watched a video named Your Old Website Is the Best Prototype of Your New Website yesterday. It talks about that you can use user research on existing websites instead of creating totally new prototype.
The video states two suggestions. The first one is to learn something from your old websites, for example, some aspect of existing website that customers like can incorporate those ideas into new design. Also, some aspects that customers do not like can figure out why then improve or change them moving forward. The second advice is learn from feature of others websites that you admire which can redesign yours.
In my opinions, once you finished your websites, you should think which one you did good in your websites, which one you should improve and understand why. Thus, you could do better in your next website. Also, when you design for your new website, you can use good part of your existing website because some existing websites solved problems might be your new websites are trying to solve.
From this video also make me think of overcoming their own weak points by learning from each other’s strong points. No one is perfect, everyone will make mistakes, even UX.