I realize that you have tons of engine experience, but I disagree that valve springs would wear out or get brittle from 5 years of simply sitting compressed.
Spring steel "wears out" from the number of compression/extension cycles it is exposed to, being overloaded, or due to corrosion and heat issues. Corrosion may be a significant factor in an engine that's been sitting - in some cases even enough of a factor to warrant replacement, but this would be apparent from a visual inspection.
I do agree that new valve seals would probably be a good idea.
Why would valve seals be a good idea?