I decided to make this mod as I much preferred the preparation style of potioncrafting in the books/TW1&2 to the version we have in game. So I made some tweaks.

It assumes you will be using the excellent Preparations mod set to refill with 'full recipe' in its options. you can also do 'base and herbs', but I've made some edits to some shops, drops and requirements to make full recipe more viable. Oils should be set to the standard 4 uses.

Also designed with drinking potions/applying oils before battle in mind, though if you want to add the awesome Complete Animations mod you can set it so you cant move while completing a drinking or oiling animation...which means you can do it in combat...if you dare.

Rough list of changes:

V.1
1. Lowered ingredient requirements for almost all potions (if anyone figures out where ingredient requirements for bombs and oils are kept, do let me know). Decoctions are unchanged (for now).
2. Massively increased the length of almost all potions (underwater breathing was the only exception, I think). Most potions now last 5min at lvl 1, 7.5min at lvl 2, and 10min at lvl 3, presuming no alchemy skills.
3. Slightly edited some features of potions so the new length of effect isn't utterly broken.

• Swallow effect reduced from 40/65/80 vitality per second to 10/20/30.
• Blizzard toxity increased to 50 (it was never meant to last that long, and you know it. this way it keeps the same degree of cool slow-mo, but restricts your other potion usage.
• Thunderbolt lvl 1 effect down to 20% from 30%, as lvl 2 also had 30%, and the main benefit of it was increased time.
• Maribor forest effect tweaked slightly as some levels of the potion only had duration as an advantage.
• Toxicity regen reduced from 0.25 to 0.025. This ensures your toxicity will not drop massively over the course of the fight, allows tox based alchemy talents to still work, and means you cant double up on potions mid fight. Also means you will have toxins left in your system post fight and will be unable to use more potions until you either wait it out or cleanse them using the appropriate potion. Not only does it give that potion a nice purpose, it also fits with the lore (Geralt doesn't exactly chug potions the second the others wear off).
• Dwarven spirits recipe requires one less Mahakam spirits. As you will be using one hell of a lot of Dwarven to craft with, giving you another way to more easily acquire it seemed prudent.
  

V1.1 Changelist

1. Edited oils effects from 10%/25%/50% to 20%/35%/50% for smoother scaling. Level 1 oils now have a real effect, and hopefully leaving level 3 oils as 50% will not impact high level gameplay. If I get feedback saying 50% is still OP, I'll change it to 20%/30%/40%.
2. Edited oils ingredients, lowered any requirements over 3 or 4, and massively lowered the requirement for bear fat, as it seemed utterly random and quite restrictive.

v1.2 Changelist

1. Fixed oils.
2. added ingredients to shops. If you want to test this, one of the herbalists I edited is the one in Novigrad, near Dandelion's inn. It seems to have worked for nekker hearts, arachas venom, golem hearts, ekimmera hide and other such rare ingredients.
3. Monsters, particularly rare monsters, have a 100% chance to drop certain things. you only come across so many golems, so if RNGsus hates you, you're screwed. Not anymore. 
3. This is basically a quick and dirty upload as I redid the mod for myself, so I could play the game, and therefore a few things are present that you may not want. Noncombat health regen is now at 9 to represent Geralt's natural inbuilt witcher metabolism. On a related note, food and water does nothing, as I RP hardcore mode (eat/drink/sleep).both removed in the unification patch version, you can easily use other mods for these and I figured keep it modular.

v1.2.1 Changelist

1. Edited some values in the shop files to make them work, as there are some typos made by the devs in the original file references. You can now buy ALL ingredients you need for potions, oils and bombs, including golem hearts etc, from master herbalists, herbalists who reside in educated, rich places, knowledgeable old nature loving coots and a certain special herb shop tucked away in novigrad.

v1.3 Changelist

1. Updated for game version 1.12, some mods may require merging using Script Merger. One I know of is the enhancement system, and I believe it only effects one of the alchemy shops, so overwriting my mod should be fine, if inconvenient. Maybe set preparations to 'herbs and base' if you come across a shop conflict, they're only edited to add rare ingredients.

v1.3.1 Changelist

1. Updated for the unification patch, removed the health regen/no food health regen.
2. Also noticed I'd added increased duration to grindstones and shrines (1h for both) in a previous version. Left that in, because honestly I can't see anyone complaining and I wanted it for personal use.

########################################### Installation Instructions ##############################################

Use the Witcher 3 Mod Manager.

If you must install manually, just extract the only file in the archive to witcher 3\mods. Script merge just in case you're using something that conflicts.

################################################Uninstallation###################################################

Just delete the file. Everything SHOULD revert.