The record among my clients is also 14 days.  It was a baby who was
stooling many times a day and fussy... until the mother stopped dairy.
Baby calmed and stools stopped for 14 days, then resumed @ one every few
days. I envisioned an irritated gut drawing a long sigh of relief before
it started back to work.

The flip side was a baby who stooled about twice a week almost from the
start.   The mother ran out of her perinatal vitamins after 6 or 8 weeks.
Baby started stooling a few times a day, and seemed to do so more easily.
-Diane Wiessinger, LC in NYS