is using a tube amp every day bad?

My Fender tubes are now 10 years old and no problems, so rock on. The one thing that does kill tubes early is throwing them in and out of vans and gigs. If the amp just sits in the same place, the tubes will last years and the amp will only go up in value. 

It's not a bad idea to have an extra set of tubes on hand.  At various points you can insert the new tubes especially in the critical positions and see if you have been missing something.  My brother has vintage fender and marshal amps and just recently discovered that his fender was getting a little tired with the current tubes after he did some swapping.  Sometimes it happens so slowly that you don't really notice it.

As Millercarbon said.. Ditto..  You Should Always Listen to your System, as Much as You want..   if your question was in reference to is it bad for the Amp?   No, actually it's Better for it!  Class A if that's the case?  Saves time on warm up, better for the tubes life, (Which that would be the only bad thing, that you would have to replace them.. and in pairs.. more frequently..).     Not sure of your Fender Exact type, yet if it generates a lot of heat, make sure it has ventilation and not a direct fan, just open air.    I love my Tube amp, leaving on standby when not listening to, and I turn it off - only if more than a week or two I'm not planning on listening to it, unless it's Winter, then I do not need my furnace on in my home.. Actually due to that I would like to get rid of it and/or trade for something with less tubes; less heat..  I love the twinkling sound they make when it warms up, (the tubes) yet it has 10 tubes on each side; r/l channels, beautiful piece, JA200 or a Jadis unit, Yet if You Like/Love Tube Sound, you will never go back to SS or Other Class B, C and such.. So Stay with it..   Just my opinion from a Tube Listener.. Jon

listening to your system >> surfing facebook >> watching cable news  :)