Experienced speakers, what's your prep time factor for a talk you consider useful, solid, and well delivered?

Assume "talk time" is just the time spent on stage, and "prep time" encompasses all of drafting, writing, preparing slides, editing, and rehearsal. (Including any work you spend on the talk proposal, of course.)

"For every minute of talk time, I spend ___ minutes of prep time."

Boosts appreciated.

A: 10 or less
6.1%
B: Between 10 and 30
53.1%
C: Between 30 and 60
34.7%
D: More than 60
6.1%
Poll ended at .
@xahteiwi the rule of thumb I've been told is, for every hour presenting, expect 8 hours of prep. Which I think is a bit on the light side.
@puck I'd say that's extremely light. I've found 1 hour of prep for 1 minute of talk to be more realistic, for myself. I really don't think I'd be able to deliver a 5-minute Ignite well with less than 5 hours of prep.

@xahteiwi I think shorter talks need disproportionately more preparation time
(per minute of content) because you have to spend so much time cutting material and making sure time isn't wasted.

I've spent 3-10 hours on a 5 minute lightning talk. I'd expect to spend 20 hours minimum on a 30-minute talk that I care about.

@puck

@chrisjrn @puck I agree on more prep time for short talks. I doubt that it'll be be more than twice as much per minute, though. Hence the width of the B, C and D options in the poll.