S.D.
I love to see questions like this!!! Instead of "why isn't my 4 week old sleeping?" every once-in-a-while a mom thinks that somehow there's something wrong with their older (almost toddler) sleeping through the night! I wish more moms were like you and realized that SOOOOOOOOO many (especially breastfeds) don't sleep through the night on the doctors' schedule.
My son started sleeping through the night without nursing around 6.5 months and only after starting solids. Here's what I think. Unless your baby is waking up to play, they are sleeping through the night. Getting up for a drink because you are thirsty or having a small snack and going right back to sleep doesn't seem so bad to me.
So, good for you for nursing so long and congrats on the long-nights' sleep! Here's hoping it keeps up :)