My title question pretty much says it all. I have three feeds with a lot of content that is extraneous to me and the training time is significant. Is training backed up by "DOWNLOAD OPML" or can it be backed up by some method yet unknown to me?
It does not. The OPML is just a XML file with your folders and feeds that can be imported to pretty much any feed reader.
As far as I know there is no way to download a backup of your training. The question is if it's needed, seems like it would be a good idea to keep a user's feed traing around for a while even if he unsibscribes from the feed.