Actually, the description of the Healthy Feature boon says that it cannot be taken more than 3 times. Although one might infer that this is the maximum bonus that healthy feature can give to Aging rolls, that is subject to debate. (Note that I think the bonus should be capped to +3, regardless of the source.)
My point is that if it's too easy to implement a few quick easy effects to get the +3 bonus, then no covenant designer in his right mind would spend 3 points of boons to get it. After all, T:Circle/D:Ring spells have been very popular as a way to avoid using ritual spells. Design the covenant walls to be a perfect circle, then inlay the inside of them with a permanent circle to cast those effects. No vis needed, no warping on those living inside. (That's why I prefer limiting this to ritual magic.)
My intent was not to clarify it for you, but rather to clarify your words so that others would not interpret them erronously, or extrapolated from them.
