diff --git a/lib/critical-path-css-rails.rb b/lib/critical-path-css-rails.rb
index 4e8bbaf..905cd8b 100644
--- a/lib/critical-path-css-rails.rb
+++ b/lib/critical-path-css-rails.rb
@@ -5,7 +5,7 @@ module CriticalPathCss
 
   def self.generate
     CssFetcher.new.fetch.each do |route, css|
-      Rails.cache.write(route, css, namespace: CACHE_NAMESPACE)
+      Rails.cache.write(route, css, namespace: CACHE_NAMESPACE, expires_in: 2.years)
     end
   end