Use your standy switch correctly to preserve the lifespan of your tubes!
A better name for the standby switch on your tube amp would be ‘warm up’ switch, cause its purpose is to warm up the tubes before you make them amplify your guitar (or noise when you’re not playing). Switch your amplifier on in standby mode and let it warm up for about a minute before you switch standby off and start playing. If you take a short break (couple of minutes), you can put your amp in standby mode so it stays warmed up. For longer breaks or when you walk away from your amp, it’s better to switch your amp completely off.