User blog comment:Bleeh/The Sims 4... in 2013?/@comment-2133744-20130517163718/@comment-2201555-20130517165908

Most games have at least a 2 year development cycle. The Sims 4 has been in development for longer, I'd say at least 3 years, given they've probably made a new engine (game engines take a while to make) as well as building up everything else. Simulation titles are more complicated than an FPS, that's why they have longer release gaps than the Call of Duty series.

They can build expansion packs within a few months as the foundation is already there, they just have to apply it onto the already existing engine.