1. Because of the item description which clearly states that you can use more of them.
("In the end it was found that his powers stemmed from the several magic rings that he had made for himself.")
2. It's not too overpowered. Most battles will be finished before you can run out of spells anyway. And with two mages they are not less strong anyway since they can cast simultaneously.
3. What will happen in BG2EE with the modified ring of wizardry? And the ring of acuity? Can't we use both? There is two ring of wizardys and one acuity... it would be stupid if we can't use them at the same time! (especially the acuity+wizardy combination)
("In the end it was found that his powers stemmed from the several magic rings that he had made for himself.")
2. It's not too overpowered. Most battles will be finished before you can run out of spells anyway. And with two mages they are not less strong anyway since they can cast simultaneously.
3. What will happen in BG2EE with the modified ring of wizardry? And the ring of acuity? Can't we use both? There is two ring of wizardys and one acuity... it would be stupid if we can't use them at the same time! (especially the acuity+wizardy combination)