Has anybody had any reliability issues with VAC amplifiers?

When you say VAC amplifiers, I'm going to assume you mean vacuum tube amps.

In that case no. Fostex was the brand. Reading/always following the owners manual helps. 

I have a VAC phi 170 IQ power amp.  I haven't put that many hours on it but have had no problems with it, not even a hiccup.

Moe, I've never owned VAC gear, but have read a number of positive comments from owners here and elsewhere over many years about reliability and great support from Kevin at VAC...to a level above & beyond many competitors. So I'd suggest searching some more threads if you don't get much response here.
I admit I was a bit surprised by your post. Cheers,
Spencer