Of course, these oil changes & valve adjustments are relative to the life expectancy of the engine. I think (hope) Jims 600 hr est is conservative, my oil ch schedule exceeds OEM specs, I am ballparking the depreciation factor to 900 hrs @ 150 hrs per year = 6 years.
The 4th-century Tomb of the Lionesses consists of a small chamber with gabled roof. The painting depicts flying birds and dolphins and scenes from the life of the Etruscan aristocracy. The 6th-century Tomb of the Hunting Pavilion shows the view seen through the transparent fabric of the pavilion.
In the case of the Etruscans, bands were put on mummies to ensure that their teeth would be preserved in the afterlife! The materials used for orthodonture were very different in ancient times. Instead of metal brackets, some ancient societies used cords made out of catgut, a fiber found in intestines.