To preface this, I've never actually had the independence faction revolt (I tend to breed/educate good rulers). So it's possible I'm missing something. But:
From what I understand, when the independence faction is refused and they rebel, they:
1. Get free doomstacks of troops to help them.
2. Wars against them aren't scored fairly; they get 7% for each province occupied, you get 0.5% or some such nonsense.
3. Once they do become independent you get strong claims on their titles.
Given the above, why would you ever bother refusing their ultimatum? Wouldn't it make much more sense to always let them go, DoW them the next day and take it all back? You can do one or more wars depending on how strong you are, instead of always fighting them all. Then there's the added benefit of the reconquered vassals losing their titles in the war, saving you the effort of revocation.
From what I understand, when the independence faction is refused and they rebel, they:
1. Get free doomstacks of troops to help them.
2. Wars against them aren't scored fairly; they get 7% for each province occupied, you get 0.5% or some such nonsense.
3. Once they do become independent you get strong claims on their titles.
Given the above, why would you ever bother refusing their ultimatum? Wouldn't it make much more sense to always let them go, DoW them the next day and take it all back? You can do one or more wars depending on how strong you are, instead of always fighting them all. Then there's the added benefit of the reconquered vassals losing their titles in the war, saving you the effort of revocation.