Mom of 5 here - I'd be interested in knowing the ages, and number of years between each child. We've always been of "the more, the merrier" mindset, and quit at 5 only because my age (approaching 40, beginning to be concerned about the increasing risks for birth defects), and simple logistics (minivan held 7, didn't want to need 2 vehicles to visit family, etc.).
We've found that a 2-3 year gap in ages was perfect for us. The older was mature enough to be fairly independent when new baby joined the family, and was ready to be my "helper". No envy, no reverting to babyisms to get attention, they liked being the big sister/brother. They also played well together as they aged. Kids 1 thru 4 fit this scenario, but surprise DS5 is 6.5 years younger than DS4. It is a much bigger gap, and he really doesn't have an agemate like the others do. Also due to the large total age span, he was exposed to many things at an earlier age than the others (scary movies, things like that). In fact, the older ones really were less exposed to things than even DD3 and DS4, since we tried to keep things as age appropriate for the entire family as we could for as long as we could. The older ones getting to school age changes everything.
I have found that the school years are much crazy busier than the baby toddler years. There are so many different activities and sports they'd like to try, all seemingly at the same time. Eventually, even if you try to double/triple up on activities (t-ball for all), the leagues begin to separate based on age and or gender. Then the kids decide to assert their different personalities and choose differently than their siblings. We've done t-ball, baseball, softball, soccer, XC, track, swimming, tennis, quidditch. The kids have joined orchestra, band, jazz band, contemporary church choir, pit, musical, drama club. They play violin, viola, cello, bass, electric bass, trumpet, tuba, piano, and sing soprano and alto. We've done 6 years of gifted math (at a university 25 miles away, 2 times a week in MS and HS), robotics, rocketclub, church youth conventions, radio academic competitions, Lego club, chess club...
Now we are down to 2 at home, approaching 1. Two out of college, one in, one going next year, one just beginning MS and loving the freedom. It will be very different next year with only one at home. We are so used to constantly consulting with one another "So how many places do we need to be tonight?" Divide and conquer is our usual MO.