live ‧ long /ˈlɪvlɒŋ $ -lɒːŋ/ BrE AmE adjective
[ Date: 1300-1400 ; Origin: lief 'dear' (11-19 centuries) (from Old English leof ) (influenced by ⇨ ↑ live 1 ) + long ]
all the livelong day old-fashioned a phrase meaning ‘all day’, used when this seems like a long time to you