diff --git a/machines/common/default.nix b/machines/common/default.nix
index 365ecf8..f9c1554 100644
--- a/machines/common/default.nix
+++ b/machines/common/default.nix
@@ -24,6 +24,8 @@
         "nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs="
         "pre-commit-hooks.cachix.org-1:Pkk3Panw5AW24TOv6kz3PvLhlH8puAsJTBbOPmBo7Rc="
       ];
+      # consider downloaded tarballs as fresh for 7 days
+      tarball-ttl = 604800;
     };
   };
 }