Downside to Increasing DB_CACHE_SIZE

I recently increased the value of DB_CACHE_SIZE from 8GB to 12GB based on my statspack buffer pool advisory.  Even after this increase, the buffer pool advisory indicates a 60% reduction in physical I/O by doubling the buffer cache to 24GB.  I have 64GB total physical memory and the "top" command shows 38GB free.  This server's only job is to host our production database.

 

Is there a downside to doubling the DB_CACHE_SIZE to 24GB?  Everything I have read says if the buffer pool advisory indicates a significant reduction in physical I/O and memory is available then the DB_CACHE_SIZE should be increased.