I second that workaholic trait for teenagers. I didn't think of it and its benefits until nearly the end, when I assigned it to a teen for a different reason. When I think of the lifetime wishes I decided to aim for, very few had five traits I really, really needed. Workaholic would have been easy to slide in as a substitute for pretty much everyone.
I did not realize birth at the hospital made a difference,
but even with dad at work, it took me no more than 36 hours after a baby's birth to get them to best friends with both parents, even with dad starting as an acquaintance. A constant cycle of play and snuggle, allowing just enough time for the baby to sleep, did the trick. Later on, dad also maxed charisma for its benefits.
For romantic interests, I used genie lamps. Mom and dad had hundreds of thousands of lifetime reward points. I purchased several lamps, had teens meet their classmates at school, never ran out of classmates, though sometimes I had to wait a couple days. The genie didn't seem to count them if that was all there was to their relationship, but with a quick invitation and conversation, the teen wished for love and that was that. This was also extremely helpful for the heartbreaker LTW, though I didn't finish it as the daughter with that wish did not make it to adult in time, which would have given her many more love interests to fill her last two spots.
The family had three motive mobiles. Twice a day, once on the way to school and once at about 9pm, everyone not looking after a baby or toddler got in the car and went to the dump. (It was the closest lot they still had to drive to.) Then everyone went back home to work on their LTWs. This eliminated sleeping, eating, showering and 90% of the bathroom breaks starting about halfway through the challenge. I should have used it sooner! The family never had a house. They lived on a medium-sized lot in Riverview (where I am most acquainted with collectibles) and their rooms were all fences to save money. The babies had a fence, the kids had a fence (later deleted when they didn't need to sleep) and the two bathrooms were walled in. Everyone lived outside. Thank goodness I hadn't installed Seasons yet.
The collecting challenges were tough, not at first, but later. There were times when I had up to four children searching for items because the older ones just couldn't find that last one they needed, even using mom's collection helper to guide them. I did resort to having children explore the catacombs on days off and at night. I'd send an adult with them who needed guitar skill or some other instrument and they'd play on the lot while the kiddo searched. (Reading what Ricalynn posted below, I also did metals 90% of the time. A couple kids did gems when I didn't want to double up searching for metals. One kid each did butterflies and beetles, but neither completed the collection and they aged up normally.)
For LTWs, I alternated between hard and easy. I didn't attempt any career wishes and I didn't have Supernatural or Seasons installed at the time. Hard was any LTW that required two or more skills maxed. Easy was anything less (heartbreaker, zoologist, etc.) This turned out pretty well and I only had a few children still at home for an extended period after they reached young adulthood. Those that did were actually a huge help with motive mobile trips and late nights in the catacombs.
For perfect garden, I actually had mom gardening the entire time until the garden was perfect. Then I assigned the LTW to a teen at the earliest opportunity. That made that one super fast.
To keep things manageable, I only had mom get pregnant when her last infant became a toddler. This actually kept the house full most of the time and there were never fewer than four kids with another on the way.
I think I know how others got such high scores: was it vampires? A random comment when I was almost done made me go "Oh! That would make learning so much faster!" That combined with the workaholic trait that slowed me down would explain some of those super high scores. I'm also dying to know how others managed the collecting better than I did.