This eventually happens, earlier for some than others cause everyone is different, but as long as its not days and days, there will always be milk there. Its like they get to the point when bf becomes on and off, or only a couple of times or even once a day, that they decide to do complete supply and demand and replace whats taken and wait for the next feed.

I to was in shock when it happened, I was a bridesmaid and didn't feed all day and that night I had my pump waiting in ready to relieve them and I didn't have to, DD1 was only 7 months but only had maybe 2 small feeds a day (plus 1 bottle). Then when she started decided she didn't want feeds I was worried there wasn't going to be there when she did, but it always was.