You should just create a new media set in "Media" and set the overwrite period to a value that meets your criterias. Then move the tapes in there (mark the tapes, right mouse click and select "associate with media set" and selectyour newly created set. With this method, your tapes inherit the values of the new media set. and keep the settings. Deleti ng the tapes or relabeling is just helping you for the moment bu not in the future, since the tapes will get overwrite protected again forever. So creating a new media set will be the right solution.
Hope that helps,
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