in the learning process or just while browsing?
Done (Ctrl+Shift+Enter) should be executed at the end of processing a piece of text in the learning process. In SuperMemo, you rarely just browse through your collection. To capitalize on each exposure with information, if you need to deal with subset of information, you do that more through subset learning (review) than through browsing. For that reason, Done is almost always executed during learning or during subset review.
