I don't poke my head in here enough! I'm still nursing dd who will be 3 in April, let's see, she's 31 months old now.
She's growing up so fast! She still nurses like a newborn, sometimes stays latched on all night long, still doesn't sleep through the night, sometimes a trial but always a joy!
I guess the answer to your original question is: once baby is not exclusively nursing, getting supplemented with solids or formula, I get to be a little more lax with worrying. After 12 months was gravy! LOL Apparently nothing I've done has harmed my supply or my dd, thank goodness.
Good luck!