critical speed in theory decreases with tilt angle
I don't make tests at critical speed because this makes the observations more confused.
If you try a hard tip probably you will see a more rapid spin decay in sleeping position than while precessing.
Sorry, I was trying to say that I think you're right to suspect tip resistance.
For a given top and launch speed, lower critical speed generally means longer spin time. You can easily confirm this with a top with an adjustable CM height, as critical speed is very sensitive to CM height, but the air and tip resitances don't change.
Since the cosine function in the critical speed formula above decreases with increasing tilt (up to 90°), that formula predicts exactly what you see in
your tops: Longer spin times in steady precession than in sleep.
It also means that if I'm seeing the opposite in my far-from-ideal tops, some factor not considered in the formula must be in play. That factor could well be rolling resistance, as you suggested.
