Do the Death Stranding main missions send you back to early locations?

Yes, the main missions do indeed occasionally send you back to places you've already been. However, you won't be able to get 5 stars with main missions alone.

Fortunately, you do not need 5 stars everywhere to proceed with the story. In fact, some places you cannot get to 5 stars before progressing with the story. You do get additional emails for reaching 5 stars, though, which may be relevant to the lore, but not game progression.

Additionally, you will gain the ability to fast travel in Episode 3 (Central Region), which will allow you to travel between the Central and Eastern Regions at will. Once you've reached the Western Region, you'll also be able to travel there as well. Even after you finish the story, you can go back and try getting 5 stars everywhere.

However, getting 5 stars does offer benefits that can help you finish the story, such as:

• Increased bandwidth for building structures, which is especially useful in the Central Region, where you'll be building a lot.
• Increased Material Storage, which helps building structures faster. Since each outpost replenishes materials automatically, having more storage capacity means you'll be able to retrieve more material upon visiting.
• Additional places to rest.
• You get the following blueprints:
  • Long Range Truck Lv 3
  • Armor Plate Lv 4
  • Extra Battery Lv 3 (Backpack)
  • Speed Skeleton Lv 3

The following 5 star rewards aren't particularly useful, but are listed for the sake of completeness:

• You get various cosmetic rewards, including holograms and colored sunglasses and caps.
• You get the Assault Rifle (HG Custom) both lethal and non-lethal. These are arguably more useful than cosmetic items, but you only get them late in the game. By then, you'll already have access to tons of similar or better alternatives.

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Note that structures degrade over time. Once their durability drops below a certain level, they become unusable until repaired. If their durability reaches 0, they disappear from the game and must be built anew.

This is especially relevant for the Eastern Region. Since you'll be spending most of your time in the Central Region, your structures in the Eastern Region may have become unusable by the time you decide to return.