is using a tube amp every day bad?

Make sure you use your standby switch often when you aren’t playing, a vintage blackface should have this depending on the model. An old Fender will chew up your tubes faster sitting at idle in operating mode than being played. There are a couple of mods you can do that can be 100% reversed to protect your amp from bad tubes and filter caps blowing. One is a simple screen resistor where needed. I suggest you find a competent amp tech, it won’t hurt the value and it can be reversed easily as mentioned above. If it hums or buzzes get it checked out, something may be wrong. If it doesn’t, play on!!

Jweilers1 is not correct, old Fender amps are not like newer or modern tube amps. They are based on very old circuits that were licensed from companies like Western Electric etc. They were not Fender’s own circuit design. When you aren’t playing them for more than 10-15 mins put them in standby mode or in the case of a vintage Champ etc, turn it off! It doesn’t need an hour to stabilize, it needs 5 mins. A Champ, that many famous recordings were made with, is simple one half of a table radio in a box, it is not voodoo like many will make you believe. Families turned their radio on, listened to their shows then turned the radio off, they didn’t leave it on, nor did they warm the radio up for an hour. When you meet a great guitar amp tech you will learn the difference between the voodoo we read in our audio hobby versus what really makes a difference in a circuit. Also, ask a good guitar amp tech what kind of power cable you should use, he should have some $2,500 units on the shelf that sound better, LOL!!!

Not if yo turn it up to 11!

Wow, talk about a totally nonsensical question.

Tubes will degrade over time but can take a beating. Dont worry about using them every day. Most likely it will take several years before you hear when a tube replacement is needed.