breastmilk question

[LissAnne]

So, here's my situation...
I nursed DS1 until he self-weaned at 13-14 months a few months after I got pregnant with DS2. Currently I am nursing DS2, who is 2.5 months old. DH and I have been discussing adoption, and I'd love to nurse then as well, but I'm not sure how it would work. Ideally, I'd still be nursing DS2 when we would adopt, so I'd just have to up my supply to meet the new LO's needs instead of having to relactate. BUT, is it true that the breastmilk changes after a certain amount of time? As in...doesn't have as much nutrients, etc? I've heard this multiple times, but obviously there are so many misinformed people when it comes to BFing that I don't know what to believe. DH asked me if that was true, because if it is, then I wouldn't want to have my milk be appropriate for a 2 yr old but not for a 3 mo old, and since my body wouldn't have gone through pregnancy/childbirth, it wouldn't know that I was nursing an infant. Does that make any sense? for some reason, it's more difficult to type it then it sounds in my head! Thoughts? Would I end up needing to supplement with formula anyway?