I've answered part of the question myself. I've
discovered the "Do not purge old files" option
in the Build menu. More importantly, when I fed
the word "purge" into this forum's search engine
I got dozens of messages on the subject. Which
leads me to an point that might be of interest
to many.

The search facility is so useful, yet it is so
inconspicuous that it almost falls out of the page.
Could the forum page be redesigned so that the
search facility is displayed prominently, e.g.
upfront, at the centre of the page?