Tiered JITs are meant to allow slower and more aggressive optimizations to be done on truly hot code. However, you're right in that they still cannot spend as much time or resources as an AOT compiler.
Re:A JVM Does That? (2011) [pdf]
by sa_su_ke_75 on Friday July 08, 2016 @09:03AM
(#12055161)
The jit must be rerunned every time the process is loaded.
In image based language like smalltalk the jit state can be saved in the image with performance optimizations.
So next time the image is reloaded the jit status is hot.
The second is more dubious... sure, a JIT compiler has information if it spends RAM and cycles on collecting that, but it also has to run quickly and fit in the runtime environment, and an AOT compiler can run arbitrarily slowly, use a whole rackful of servers, and can use PGO without incurring any profile collection costs at (normal) runtime.