I disagree with number 3, sometimes it's nearly impossible to get the desired effect with just a few frames. If it's a quick motion, like blinking, sure fine, but things like slow motion and particles take many many frames. Cherry blossoms fall very slowly, it would look absolutely messed up, unrealistic, and break a few of your other rules, if they fell quickly to fit your speed restrictions.
Also I like watching long, looping avatars, if it's a complex motion, they flow more fluidly.
Also I like watching long, looping avatars, if it's a complex motion, they flow more fluidly.