Expeditions run for anywhere from 4-8 weeks, but they usually only take a dozen hours or less to actually do. I've been able to dedicate a few hours on a weekend and do the whole thing in a session or two. If you're familiar with the game's systems, it makes things easier, since you already know what to do to accomplish most of the goals. Plus, you can now convert an existing save to a expedition save and bring some of your equipment and supplies over. Once you're done, you can convert back and bring your stuff back, along with any new things you found. They've made it pretty easy to engage with.