Although battery saver saves a lot of battery power, it is not recommended to keep the battery saver on all the time. It helps you save battery power, but there are a lot of consequences. For example, it stops all kinds of background synchronizations. That said, you cannot upload or download files through any cloud storage service, such as Google Drive, OneDrive, etc. Apart from that, it disables a lot of background processes and services, making several programs half-baked when it requires background data synchronization.