the "blister" analogy is not correct. In the case of a "blister" forming around a wood sliver or some other foreign object, the size of the object does not change. Therefore once the body has added enough serous fluid to cushion the skin from contact with the foreign object, the blister doesn't get any bigger. However, in the case of string implants, the skin also controls the size of the "string ball". First the body adds serous fluid to cushion the breast skin from contact with the string. But as the skin moves away from the string, the "string ball" is allowed to "unravel". This makes the "string ball" grow physically larger, and sets off a fresh cycle of the body having to add more serous fluid to cushion the breast skin again by **77** it farther away from the now larger sized string ball. This creates a "positive feedback" situation where the bigger the breasts grow, the bigger the string ball gets, and the bigger the string ball gets, the bigger the breasts grow!
At some point though, the "outward pressure" of the string ball" and the "inward pressure" of the skin elasticity will theoretically balance each other and the growth cycle will stop. This explains the "inverse logarithmic" growth characteristic of string implants i.e. my own implants grew 3 inches in the first 6 months, 1 1/2 more inches in the next six months, 3/4" more in the following 6 months, and 1/2" in the 6 months after that, and are still growing albeit at a (thankfully) barely perceptible rate. I think that if you take a really close look at recent pictures of Minka you'll see that she's also continuing to grow, but at a very slow rate.
However, it is very easy to upset the body's fluid balance i.e. anything which causes the body to retain fluid will increase the amount of fluid inside the breasts as well - but which doesn't go away when the retained fluid is eventually removed from the rest of the body. This fact essentially guarantees that string implants will continue growing forever, unless something else specifically removes fluid from the breasts like the doctor drawing it out with a hypodermic needle!