To satisfy my own curiosity, I reinstalled OS X Snow Leopard today.
It took about 48m to install the OS. I excluded all printer drivers, foreign language fonts, and translations.
You can’t trust the estimated time to completion. It started by reporting only 17m. After 17m, it changed to 18m, at which point I quit watching. Returning later, it reported 5m remaining, and after 1m reported completion.
One reason for a faster installation, too, is that the installation media is not verified as it was in Leopard.
This was on a 2.0GHz Core2Duo Mini.