Most I've been on are 5 a day which I find is a bit too much, especially after a day or 2. I like to have a little more time to just relax, and my ears appreciate the break. I tend to skip late afternoon dives in favor of a night dive. If it's 3-4 dives then I'll usually do them all as long as my ears are cooperating.
If there's a night dive every night I don't do them all, and most people don't seem to, especially as the week goes on. Some people don't like to night dive, and as for the rest - it always sounds like a good idea until you're warm, dry and fed and someone has stuck a bottle of wine in front of you...