to 4 hours, I would never leave any nappy on that long during the day, pocket, fitted or sposie! All of mine have been changed every 2-2.5 hours during the day. Mia gets changed 2-2.5 hourly except at night when she wears her night nappy for about 8-10 hours.
All the pockets we used were well stuffed and his bum felt barely damp when I changed him. Perhaps I put more stuffing in them than other people do? The inserts were never absolutely soaking wet either.
I don't see the need to change a nappy unless it needs to be. As long as he was comfortable and the nappy wasn't hanging down by his knees! Which it never was.
I can't see what is wrong with going 4 hours - why change a nappy more often if it isn't needed?