I take my 2 out about every 1.5 - 2 hours or so when I'm home. They are 8 and 5 yrs old though so they should be able to hold it longer, but the 5 yr old has just been here a week and I want to make sure he's getting plenty of opportunities to suceed!
I don't take them out at all during the night (usually 10:00 p.m. - 5:30 a.m.) - thank goodness they do fine through the night!