If you play a large household, challenging career &/or financial goals, multiple households, out-of-household interaction/collection, etc. Up your challenges in your households.This also provides potential for interaction with other players, etc.
On the forums you can find many threads with gameplay or build challenges that can be very challenging. Some expansions even add careers, skills and a lot of interesting options. They can ad an incredible amount of interest and depth of possibilities for play, depending on the particular pack and what it adds.
