And now a parenting question

I never, ever thought I'd do it, but thus far I breastfeed my baby entirely on demand. We have yet to be apart for more than 3 hours at a time (note to self: maybe that explains why I can't get enough work done even with a babysitter ...). She also has no real sleep schedule - I just try to make sure that she's not awake for more than 2 (max 3) hours at a time. And she's a good eater and sleeper, so it seems to be working out.

Tonight she started crying when I was at my father's and he asked what was wrong. I told him she was probably poo'ing (yes, she screams. Lazy, lazy) but I'd try feeding her. And I must have said something about "Well, I feed her whenever she screams and I only feed her when she screams" because he looked very concerned and told me I was forming all the wrong associations if I only feed her when she cries ...

When she was little I could pick up her rooting cues and know she was hungry, but now she seems to switch rapidly to loud cries when she is upset about anything. I do remember years ago a friend telling me how glad she was that her babies cried when hungry "or she would never feed them" and I remember thinking the statement was a bit odd. But now I totally understand. Between keeping her clean, well-rested, warm enough, cool enough, stimulated but not over-stimulated, I just don't have the energy to focus on keeping track of how often she eats. I know she'll cry when hungry, and I know I can feel it if she goes a really long time without eating. But am I forming some awful association for her? All advice appreciated.