Can't fully answer but it is definitely more than a few minutes.
When we were in Panama in April we took an excursion thru the ship to do a partial. We started on a bus to the middle lock then a ferry on to the Pacific. The length of the whole excursion was to be 6 hours but because the ferry had to wait for an oil tanker at the locks instead of being on the canal for 3 hours we were on for 6 hours. So our ship was 3 hours late leaving port.
Star Princess 2005, Sun Princess 2005
Caribbean Princess 2006, MSC Lirica 2006 , NCL Pearl 2007, Majesty of the Seas 2008, Carnival Destiny 2008, MSC Lirica 2009, Carnival Valor 2009,Carnival Legend 2010, Carnival Liberty 2010,Carnival Fantsay 2011,Carnival Valor Feb 2012, MSC Poesia Dec 2012, MSC Poesia April 2013, Carnival Legend Nov 2013, MSC DIVINA Jan 2014