First, I want to say that you are awesome for nursing while working full time. I really admire women who can make that commitment. I don't know if I'd be able to do it.
In regards to nutrative nursing (note: I am *not* a health professional), I think it depends upon how much other food your baby eats and what type of growth spurt they may be experiencing. Also, I noticed that my baby nursed a lot for comfort while going through new developmental stages (learning to walk, realizing object permanence, etc.).
You may want to check out the book, "Mothering Your Nursing Toddler." There is a section for working mamas in there and it's an interesting read.
Personally, I only have limited experience with pumping, using an Avent hand-pump. I have always had a lot of milk, but now that I rarely use the pump, my breasts don't really respond to it. I can only really pump if DD is nursing on the other side which doesn't work well now that she's old enough to "help."
My DD is 19 months old and still nurses a lot. I am home with her during the day, so she has access pretty much any time she wants, but she will sometimes go for 8 hours without nursing. Other times, it seems like it's all the time.
Some days I think she wants it for more nutrition - when she gets really serious about nursing and is very into it. Other times, she is just "checking in" or reconnecting with me and pops off a lot to check out what the dogs are doing or whatever.
Lately, she's been nursing a lot at night. We co-sleep, so it's easy access but it does make a long night for me sometimes. She's working on her last set of molars and has been in a bit of pain so I am sure that's why she's been pretty needy lately. Also, she's always had high sucking needs. She has a callous on her thumb because it gets a really good workout too.
I don't really see DD weaning herself anytime soon. She really likes to nurse. Sometimes, I wish it was just a morning and bedtime thing, but for now I am just going with the flow.....of milk. (
Sorry, couldn't resist the pun.) I do love the way she pets my arm when she's getting her milkies.