I take the approach that the Download Folder is a temporary holding area for that which was just downloaded and that ideally it should be empty. I find searching through a full folder of mixed items inconvenient. If I need to keep any of the documents that have been downloaded I move them into an appropriate folder elsewhere on my Mac.
Precisely because the d/l's folder tends to be a junk collector, I've got Safari > Prefs > General > File download location set to my desktop, which gives me immediate impetus to move those d/l's I want to save to the location in which I want them to "live," and those whose purpose is served immediately or in short order, to the trash.
Afterthought: Every once in a while, a d/l winds up in my d/l's folder despite my pref, so I know to look there if one is missing from my desktop.
