Noise when turning on/off tube amp?

Sorry Snooker14, I need to learn not to read/respond so late at night. Integrated tube amp. (pre-amp and amp controlled by one power switch) does not permit you to perform the recommended on off schedule. Now back to your question. Three years is about the normal life span for a amp tube....you can squeeze a tad more out of pre-amp tubes. They will still work, but the sound quality and sound stage starts to degrade. It is not recommended that you keep a tube rig 'on' all the time. The tubes can be consumed in a few months. Try a new set of tubes for your rig...it's time anyway.
Regards

Snooker14, What power tubes are you using now? What kind of music do you listen? Which you prefer? Oil caps in your SLI80? I ask so that the advise will fit better to your taste and setup.

I use KT88s in my Rocket-88 and have tried JJ Tesla and Svetlana SED(c) logo. I have found the Svetlana softens the top a bit and enhances the midrange with less bottom end compared to the JJs that have a more balanced presentation but can sound bright in the wrong setup. I prefer the Svetlana sonic signature. This is a listener speaking not an expert.

Thanks again for the responses. The tube life is probably near the end as suggested. Funny enough, the noise I referred to has stopped completely, no explanation. I do have oil caps, and will look at different tubes. Thanks again....