> Integrating NGEN in your application’s installer might be a challenge; auto-NGEN addresses this challenge by performing NGEN automatically if runtime-generated profiling information deems fit. When your .NET 4.5 application runs, the runtime generates assembly usage logs which are examined by an automatic maintenance task that runs in the background when the system is idle, and generates native images for frequently used assemblies.
(This maintenance task might also choose to evict native images for assemblies that have not been used for a long time.)