My toddler (almost three) is still nursing! She doesn't get much milk and uses it mostly for comfort, but she sure is attached to the breast. I'm glad she'll be getting more good milk soon! it will be so good for her. I don't think she'll nurse a lot (porbably not more than three times a day), but I could be wrong!
I have never tandem nursed before and this will be our fourth baby. I'm planning to let the baby nurse first at a nursing session, and let the toddler nurse afterwards whenever she wants to. I'm also prepared for the possibility that it could be uncomfortable, and the toddler will get cut off! I have heard that some women find tandem nursing a bit unpleasant because of the differences in sucking patterns, and it just kind of wears a woman's breasts and patience out. But I think for the majority, it works great! I think that like everything connected to nursing, it will take adjustment.
Sometimes the older child stops wanting to nurse when the milk really comes in, too, seeing it as a baby thing, or because the older child does not like the taste. Impossible to predict. I'm really curious what my toddler will do. I'm really curious how I will like tandem nursing.
Good luck with your tandem nursing. I'll be interested to hear how others are doing with it, after all our babies are born!