Vintage Tube amp worries

The amps are VAC.
Thank you to all who post and your expertise. 

5 years not powered up doesn't sound like that long. As mentioned I believe it depends on the brand and quality of components used. I have seen older tube amps sit for 10-15 years and then plug right into the wall (no variac) and power-up with no problems.

What brand are the amps?

When long in storage electrolyte in electrolytic caps eats out dielectric (aluminum oxide) lowering breakdown voltage.  Presence of voltage rebuilds dielectric.  Power amps thru variable power transformer starting with 50% and increase voltage to 100% over at least one day.  I'm not sure if low voltage can do any harm to tubes.