Your weight on the scale, the results from your inbody or better yet dexascan all give valuable data. But so do your progress photos. Body composition is a huge aspect to longevity and muscle mass is protective against injury and diseases of aging such as cancer. However, vanity is also important. You want to make sure you are feeling more and more confident about what you are seeing in the mirror.
Daily reminder to progress your lifts. The reason we do the same exercises for weeks in a row is so you can get better at them. Increasing the weight you do on an exercise is one of the most effective ways to build muscle.