How to restart tube amp and pre in boxes for 2yrs

For a cheap way to be safe, plug them in and turn them on for only a moment. Fast on off for LESS than a second. wait twenty minutes or so. Flip them on again, but leave on for three seconds, then off. wait an hour. Turn them on for a thirty seconds, then off for a few hours. They should be good to go.
This is a 'sort-of' variac approach. the caps need to be babied, and the momentary turn on, then longer do the same job, only for free.

i read a caution that tube amps need to be hooked up to a speaker load at all times when turned on. can anybody verify this?

Most tube amps are supposed to be operated only w a load (speaker or resistor across outputs) but I have no idea if this applies to the momentary on-off approach Elizabeth advocates. Best approach is to use a variac and bring the voltage up very, very slowly to allow the capacitors to "re-form" (whatever that means). 2 years is not that long, you might want to ask Chris @ Parts Express who does a lot of modification work on SF gear and I think used to be involved with that company (maybe co-owner??).

Swampwalker, great idea! A variac is the way I do it with equipment that's been off for a few years or more. I will usually pull the output tubes, and monitor the voltages from the tube sockets. Contact the manufacturer just to make sure it's safe to pull the output tubes. With the output tubes pulled I only run the variac up to 110Vac. Internal voltages will be higher because you have the output tubes pulled and you don't want to over voltage the caps. Or let a tech do it for you. I'm on the west coast.