@eugenesv: Please don't bump multiple threads on exactly the same subject to add a +1. One is enough. Additional bumps will be merged/deleted to keep things tidy. (Also so we don't end up having identical/redundant conversations in two or three threads, or risk leaving things unanswered in one because we answered in another, and then people find the other and think we ignored the question.)
Monitoring for changes in temp is done for FTP sites but not archives currently. We may extend it to archives in the future.
Temp files may be cached for a few minutes in case you open the same file again. If the file is still there after you fully exit Opus via File / Exit Directory Opus (do not just close all windows; that isn't enough) then that may be a bug, and is worth reporting in a new thread with details on how to reproduce it. It could also happen because something else still has or had the file open and blocked its deletion, in which case Opus would try to clean it up when run later. Opus periodically looks for old temp files it has made and removes them.