Being as you have to carry everything with you and can't use hostelries is it just the case of sitting in a tiny tent eating dehydrated food for 16 hours?
Mainly, yes, but the time always seems to fly by.
Firstly, just getting the tent up, gear stowed, getting changed, water collected, food made, score checked, map examined for next day, bike cleaned and fettled, tent down, bog visited, breakfast drink made, kit repacked etc takes up quite a bit of the time.
Then, bear in mind you are knackered (if you've been trying) you'll generally want a good long sleep.
Then bear in mind that you'll either be camping near your mates and chatting, or making new mates and chatting, which also takes a good while.
So really, 16 hours isn't that much.