In my humble opinion normal HP potions/MP ethers/HP-MP elixirs is completely wast of space for high level (when You have over 4k MP for example), very few hundred MP with this recast times is useless. Better use this recasts to buffing Your stats with potentials or inflict status effects with status potions.

Item level 70 X-Potion is the King with 520/650 HPs and under 2 minut recast time but forget about mass craft it. Better to get luck drop from Amdapor Keep, Coperball Mines (hard), Chamber of Horrors or for reward from lvl 50 few main story quests if You take time to see what offer and dont take allagans in rush.

Hi elixir can be life saver every?: 7 minuts?

Maybe Dusken Draught for Storms can be life saver with 360 HP and 1.20 recast but is Unique untradable... = once

For low levels yes is usefull and life saver with good rotation of cross-class healing skills. Hi potions and Hi elixirs best recast/price like.

Hope so help a little.

Salutations.