You can do all in about 30 mins each with 3 exceptions.
Boboli garden: can possibly see most of it in 3 hours but if you catch a nice day you might end up wanting to stay much more
Uffizzi: 2 - 3 hours
Duomo attractions 2 hours
This is the time to see the places and don't include waiting in line time. Also it's my opinion. Art LOVERS may spend slightly more time at each location.