I was under the impression her body would only at most last months at most and the family has found a way to fund the care (outside of the 2 weeks it took them to get her moved)
Most people when put in the position do not feel this way an I have never considered this could go on for years.
There are some cases where bodies of brain dead patients lasted for years.
It does sounds like Jahi's body is in poor shape and deteriorated badly. So I don't think she will last years, but who knows.