my personal opinion is it should stop at around 2. but honestly, what ever you and your child are comfortable with.

my son has self-weaned himself at 18months. be prepared to have some sadness over it. i know i feel sad over it.

The answer is...when you are ready! I breastfed until my daughter was just over 2. I explained to her that she was getting to be a big girl my milk was almost gone. I kept telling her this for a couple of weeks and then one night told her it was all gone. She had a sippy cup of milk at storytime instead! It was very painless really! The routine stayed the same, but the"booby milk" was gone. She kept patting my breasts as if to say "bye bye"but we had no real dramas! The end time is up to you! You have exceeded the norm and provided your child with the best. Only stop when you are ready!

As others have said keep going as long as you and her want to. The natural age that a child self weans is anywhere from 2yrs to 7yrs with the world average being 4.2yrs. there's so many benefits to keeping going. My youngest weaned at 3yrs +3mths. It was very rewarding and he is extremely healthy and active.

It's entirely up to the two of you! The WHO recommends b/f for at least two years, and the health benefits continue for as long as you do it. It also has benefits for the terrible twos, as I noticed! However for me "about 2 years" felt right, so I stopped feeding DD1 at 2&1/3 and DD2 at 2&1/2. If you are coming up to that point, can I recommend a long run in before that foot goes down? I was preparing my DDs for months before I finally stopped, telling them "soon/when you're a little bigger/when you're big, you wont have baby-milk any more", and when I finally stopped, neither put up much of a fight, as they were happy to be "big" and were happy with the new toy they had been promised!

When YOU decide to. This is your decision and can't be made by anyone else.  I had a friend who b/f until her daughter was 2.5.  She enjoyed it as did her daughter.  You stop when she's weans herself, or when you've had enough.

Good on you for b/f for so long.

When you want to. 

There's no right age to stop breastfeeding, and if it's working for you, then do it.  You might cop some flak from other people if you tell them about it, but it's not disgusting or inappropriate or anything, especially if it's night feeding, and not in public.