MY DS has never slept longer than 40 mins at a time in the day either. In fact, of 10 women (and 11 kids) in my mothers group, ONLY the twins sleep longer, and I'm sure it's because they are not alone.

Two of the bubbas don't even do 40 mins so I'm thinking myself lucky at the moment.

DS has 3-4 40 min sleeps a day. I know CHN's say it's not enough, but it's just how he works so it's fine! He's happy and rested.

Whatever works for you.