We like to be in the area for 6 ish days. We typically plan 5 days for the parks. We prefer slow/low season since we like the shorter lines. We love to break up our trip with a rest day. We head to the beach, do a little dinking around the area, check out any fun things we might like to do, try a restaurant that's recommended on Yelp without having to worry about interfering with our park time, or just laze around and swim a little.
The break during the middle of our trip gives us a nice break and helps us rejuvenate. We've done our "break" several different ways. We've taken the whole day and done basically nothing, we've skipped DLR in the morning and headed to the beach, then back to DLR. We've headed into DLR in the morning and then out at noon or so to go to the beach and out to a good restaurant and then early to bed. Our family consensus is that we like to go to DLR first and then head to the beach. It fits our family pattern really well.
Like I said above we like low season and shorter hours - our kids stay on a more regular sleep schedule, nobody gets super cranky, we don't feel bad about leaving DLR early (by 7pm) because we've done everything we've wanted to do that day. We spend some down time in the hotel room and decompress. It works for us.