The length of time you can marinate chicken in soy sauce depends on the type of soy sauce used and the recipe you are following. In general, marinating chicken in soy sauce for 30 minutes to 2 hours can enhance the flavor and tenderize the meat, but marinating for too long can result in the chicken becoming overly salty and mushy. If you are using regular soy sauce, which is high in sodium, it is recommended to marinate the chicken for no more than 2 hours. However, if you are using a low-sodium or light soy sauce, you can marinate the chicken for up to 4 hours without it becoming too salty. It's important to note that if your marinade contains acidic ingredients, such as vinegar or citrus juice, marinating the chicken for too long can result in the meat becoming tough or mushy. So, always refer to your recipe for the recommended marinating time and ingredients, and adjust as needed based on the type of soy sauce and other ingredients used.