"Delete no longer needed temporary containers 15 minutes after the last tab in it closes" is a default setting. This is not an issue I've experienced in the 3+ months I've been using this extension.
Are you sure you didn't accidentally change it?
Are you sure you didn't accidentally change it?
Edit: Apparently HN strips box drawing characters. Imagine the output of `sparklines 6 15 7 5 2 1 1 4 3 1 1 1 1 1 1 1`.