should search ring contain duplicates?

["Drew Adams" <drew.adams@oracle.com>]

Each successful incremental search adds the search string to the search ring
(as the most recent entry), even if it is already in the ring past the first
entry. Nothing prevents the ring from containing multiple copies of the same
string, which seems wasteful (and useless). At the limit, the search ring,
regardless of its length, might contain as few as two different search
strings.

Shouldn't `isearch-update-ring' (in isearch.el) add the latest search string
at the front of the ring but remove it elsewhere in the ring? The result
would be a more useful ring.