It is generally safe to leave a VPN on all the time, but it can use some of your device’s resources and battery life. If you are not using the VPN for a specific task, you may want to turn it off to conserve energy. Additionally, if you are connected to a VPN server that is not physically close to your location, it could slow down your internet connection.
However, if you are using a VPN to protect your online privacy or to access restricted content, it is generally a good idea to keep it on at all times. Just be aware of the potential trade-offs in terms of performance and battery life.