It's a requirement going down Pikes Peak to use your engine in the lowest gear, along with breaks as needed. About midway down, someone checks your break temperatures, and will require you to stop if needed.

My Saturn, lacking a way to keep the automatic transmission in anything lower then second gear, led to a 30 minute stop.

For some odd reason, I'll shift down my Saturn all the time on big hills around here. Not sure who I picked the habit up from, but I started doing it more after learning how to ride my motorcycle.