experimentally increase dbuild caching length

it's not so much that we need longer to do postmortems, it's more
that I'm hoping this might sometimes speed things up a bit, if
cached things can be used more often?

Author: SethTisue

common.conf

@@ -144,15 +144,17 @@ options.resolvers: {
   04: "dbuild-unchecked: https://scala-ci.typesafe.com/artifactory/dbuild-unchecked/" // for sbt plugins not available on ivy (they'll fail the pom check on the `dbuild` cache repo above)
 }
 
-// we don't have enough disk space to keep stuff longer
+# new behemoths have much more disk space, so let's try keeping stuff
+# substantially longer (2 weeks instead of 4-5 days) and see what
+# the effect on disk space usage is, starting March 17 2018
 options.cleanup: {
   extraction: {
-    success: 96
-    failure: 120
+    success: 336
+    failure: 336
   }
   build: {
-    success: 96
-    failure: 120
+    success: 336
+    failure: 336
   }
 }