There comes a time when it's no longer viable to
keep old machines
running. Computers aren't anything unique in this regard.
To be a wiseguy somewhat, I'd say it's summer.
Keep your more precious beasts off when ambient is
above 80 or certainly 90 degrees farenheit.
Personally, I don't think continuous duty at all for anything >10y-o.
Use commodity PC's for work not itself of historical significance.
John A.