I'm not sure I understand this correctly - I know that it's impossible to run out of milk as it's constantly being produced, so how/why is it that introducing formula or feeding to too strict a routine can have a negative effect on the supply of milk? Surely if it's neverending, it's... never ending! I suppose it has to end sometime (e.g. when the child weans) but how can you end up with "supply problems" when there is still some stimulation there?