Umm, I think I agree with the others. This is such a severe nerf that it borders on an outright ban. It also means that wearing a ring of sustenance for more than three weeks will result in instant death should it be removed (due to going without water for 3 weeks).
Similarly, such logic would make any magic item that allows for survival without air worn for more than a few minutes instant death should it ever be removed. Unless, of course, the PC can hold their breath for 5+ minutes . . . .
I tend to see such items as providing sustence directly to the body, without the need for a digestive or respiratory system. The needs of the body are innately sustained, such that the need for food, water, even air, is slowly lessened, until no longer does the body need to breathe, drink, or eat. Having no need for such, why would they body experience penalties? That would be like applying penalties being in high altitude due to the fact that sea level is considered high altitude compared to somewhere on the planet, so certainly high altitude penalties must apply - even if the character has lived at sea level all their life and has neither intention nor need nor even the means of leaving sea level.
Their body does not need to adapt to lower air pressure, so why apply the penalties? Similarly, in your example, their body does not need the food, water, air, so why apply the penalties for their lack? Shouldn't you also, by this logic, apply penalties for not drinking blood, as some variant vampires have penalties for such, and the player may one day perhaps maybe meet such a vampire and be bitten / changed?
As best I can tell, that is the type of logic you are using in applying penalties to your players when they use Rings of Sustenence or Amulets of Adaption. If you wish to ban the items, then just do so. Don't place arbitrary and unreasonable restrictions upon their use.