How does replenishing Alchethe items like potions work

From here

If you meditate with hard alcohol, then any potion, oil, or bomb (basically most quick-action consumables) you've previously crafted will refill. This doesn't work obviously for mutagens and components Just be sure to meditate in a safe spot. Wine doesn't work, it has to be hard liquor.

If you craft a mutagen potion, it will forever refill in this way. This is a direct response to Dragon Age: Inquisitions need to have you gather herbs endlessly to keep making health potions. You only have to craft a potion once.

Well there are tons and tons of diagrams for new potions so all those ingredients can go for those new potions. And now you need a lot more ingredients to make a potion so it isn't bad gathering ingredients.

If you don't need them go ahead and sell them for some extra orens.

I experimented a bit myself with decoctions, and found the following about the mechanics of them.

They do replenish like potions do, as already stated in another answer. They also have vastly greater durations at around 30 minutes. But the way toxicity works is fundamentally different than with potions. The toxicity from decoctions doesn't seem to decay, it was set to a fixed 80/100 in my case (without any skills in the alchemy tree).

This means that it is impossible to have two decoctions active at once as it would exceed the maximum toxicity value. It also means that while using some potions is still possible in addition to a decoction, it is severely limited. In my case, only potions with 20 toxicity can be used, as that is all that is left to the maximum of 100. And each potion use did cause a signficant health loss as I hit the maximum toxicity value.