I've left germini and lily out of water for a couple of days, used calla and anthurium in arrangements with stems out of water and they have lasted 2/3 days. When I was at college I left a carnation buttonhole in a plastic bag in the fridge to see how long it would last - got bored of waiting for it to die after a month!

I always thought of paeony as really fragile but last year bought off an English grower for the first time and he said they were tough as old boots, could go for days without water when in bud. Have never tried that though, they get used too quickly