i made it through pregnancy still nursing. DD is 3.5. for me, it only hurt-hurt the last few days before i went into labor. now that DS is here, there have been times that i've felt the "aversion" but i just limit her time. i remind her that to her the milk is a nutritional snack, whereas for DS, it's his only food, and he needs it to live.
but that doesn't really answer your question. i don't know. in some ways i would have to say that aversion to nursing is possibly a sign to stop. on the other hand, you are very close to the finish line. for me, i think i felt a little guilty being pregnant at all, even though DD was 3 yo. i just made a commitment to myself (and her) early on in the pregnancy, that i was going to keep nursing her. i told her there would be lots of good milk once the baby came.