Amps are a lot like children. They need to feel wanted and loved.
I know you're worried that you might be spoiling them. But as long as you keep them away from junk tubes, and give them a little reassuring pat on the cabinet every now and then, you're not going to spoil your amp.
So go ahead. Tell your amp that you love it. It'll be happier, and you'll have better tone.
And remember to clean off the beer spills and dust, man. No one wants to hear your amp crackling every time you turn a knob.