dev_status: Increase max age

Increase the default max age so we're more likely to get 10 builds for
infrequently run builders. This means we'll get more falso negatives,
but that's better than getting false negatives.

Bug: b/339638439
Change-Id: Ibff2a39181edbdb931e2a93291732df273c9d45e
Reviewed-on: https://pigweed-review.googlesource.com/c/infra/recipes/+/209978
Reviewed-by: Taylor Cramer <cramertj@google.com>
Pigweed-Auto-Submit: Rob Mohr <mohrr@google.com>
Commit-Queue: Auto-Submit <auto-submit@pigweed-service-accounts.iam.gserviceaccount.com>
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>
Presubmit-Verified: CQ Bot Account <pigweed-scoped@luci-project-accounts.iam.gserviceaccount.com>
diff --git a/recipes/dev_status.py b/recipes/dev_status.py
index 3fed437..1832afe 100644
--- a/recipes/dev_status.py
+++ b/recipes/dev_status.py
@@ -43,6 +43,7 @@
 PROPERTIES = InputProperties
 
 DEFAULT_MIN_BUILDS = 10
+DEFAULT_MAX_AGE = datetime.timedelta(days=21)
 
 
 def _make_dev(bucket_name):
@@ -63,9 +64,7 @@
 
 def RunSteps(api: recipe_api.RecipeApi, props: InputProperties):
     min_builds = props.min_builds or DEFAULT_MIN_BUILDS
-    max_age = props.max_age.ToTimedelta()
-    if not max_age:
-        max_age = datetime.timedelta(days=7)
+    max_age = props.max_age.ToTimedelta() or DEFAULT_MAX_AGE
 
     bb_cfg: bb_pb2.BuildbucketCfg = api.luci_config.buildbucket()