Is it important to clear buckets?


My app keeps inserting documents to buckets.
It never deletes them, assuming that the data will be rotated once it reaches the max ram limit assigned to the bucket.

But what effect does full buckets have on speed of data retrieval?
Do I need to make sure documents are deleted once they are no longer needed to maintain performance?
Is there a difference in this aspect between Ephermal and Couchbase buckets?