GO FOR THE EYES BOO! GO FOR THE EYES! RAAAARGH

You can test yourself at the expense of actually getting sleep. As you settle to sleep set a timer and hold a teaspoon (or similar metal object) in your hand hanging out of the side of the bed over a metal tray. When you fall asleep the spoon will slip from your hand and clatter, causing you to wake. You can then check how long that took.

Me mad, me wizard, me speaks