True also of The Witcher (especially) and the Witcher 2. I had all the potions I needed, and more made, I had an inventory stuffed full with alchemy ingredients, and those I couldn't carry packed in huge quantities in my luggage at the inns. There wasn't any point in herb collecting for me at-all after the end of chapter 3 in The Witcher. Still did though because I could stuff a few dozen more of "that one" into the ingredient slot before it too was maxed out.But still...the enhancements are not unlimited.
When you have created all the superior potions, you have a lot of herbs around which are pratically useless.
The same happened (more or less) after the end of Chapter 1 of Witcher 2... had all the potions I needed for the rest of the game and I only collected ingredients because they were there. (Crafting materials I was collecting and using throughout the game - but I had huge stocks of some materials in the luggage - there is also a little overlap between these).