How many years long is a billion hours?

114,079.7189 years

A solar year is 365 days, 5 hours, 48 minutes.

Which calculates to: 8765.8 hours

1,000,000,000 / 8765.8 = 114,079.7189 years

Bear in mind that the length of the solar year changes over huge periods of time, so any calculation is approximate.