I nurse twins who are almost two and it sounds much the same with Jacob as it is with my girls -- it's sort of a snuggly Mommy/baby time, but I am never sure how much they are getting in terms of food! I know it's less and less, and each evening I literally wonder if that will be the last time. I have decided to just let them keep going until they quit (within certain limits...) and not worry about weaning, etc. As we just do it at night it is not disruptive to others, and nobody has been critical of my decision to BF on an extended basis (to my face, at least!).
I do plan on waiting to get pregant again (if we do) for at least a while after they stop, and not until they are 3 or 4. I think 3 would be my minimum age dife ference -- as you said, at that point the older child would have a sense of what was going on and be able to be independent and a little helpful! Many women with whom I was pregnant two years ago are now having their second babies, and what I hear most often is that they can feel torn between the needs of their babies and toddlers.
Another thing to consider, which is more important than many people might consider, is that especially after extended breastfeeding, your body really needs to replenish its mineral stores after a pregnancy. You will do your next child a great service, actually, by building back up between pregnancies, which you can't fully do while nursing. There are different theories as to why oldest children tend to be the smartest, and that they "get" all of the mother's nutrient stores is a strong one.
I plan on taking some time after the girls are finished nursing to literally "bone up" with mineral supplements, eat well, and most important, enjoy a baby-free body for a while! If my girls nurse through the summer, August will be 3 years since I have been pregnant/nursing...I'm thinking that my husband might like a baby-free period of time before I take the 3-year plunge again! Maybe if you encourage yours to look at it that way, your husband will be more amenable to letting you have some prep time for baby # 2.