Measuring plan eviction
There's an XEvent for that:


  query_cache_removal_statistics
  
  Occurs when a query plan is removed from the plan cache and the
  historical statistics for the object are about to be destroyed


So something like:

CREATE EVENT SESSION [PlanCacheEvictions] ON SERVER 
ADD EVENT sqlserver.query_cache_removal_statistics(
    ACTION(sqlserver.sql_text))


Also if your plan cache has a large number of single-use plans consider setting optimize for ad hoc workloads.