I recently posted on the Seam forums about a performance issue with having a large amount of entity beans sitting around in a conversation causing a significant delay at the end of the rendering phase. I tracked the delay down to entity bean passivating.
So use case question. Why do you have so many Entity Beans. If I am on a web page, there is only so many records I could view at a time. If it is a search, which returns a lot of records, why not using pagination to only get a small amount for each page. Maybe a user can see 25 records in a list at a time.