I was thinking, now that you have the Flasks it might be a good idea to reward someone for leveling with a set of flasks rather than just “Filling Up” their flags. I know I have levels when some of my flags were already at full or close to it. IT felt like a missed reward. The Flasks would allow the player to enjoy the reward you mean for them to have for sure.
So to summarize; give a set of flasks when they level as a player rather than jut up their flag counter.