How big a game changer is additional options?

Aside from 150 flames which I didn't know didn't drop, flames are tiered to drop from their respective level bosses I believe. So Farming horntail for 140 flames is seeming to be what I'll be doing if this is the case.

So...Horntail, pink bean, and the bosses had their HP increased? I know it was said that 140 flames are 50m, but what does that mean as far as a percentage? Am i going to get a flame within 10 runs? 5? 3? 1?