Other than important new mail that I leave in the server Inbox so it's at the top of the info hierarchy, and list mail that I keep in subfolders and periodically expunge, I regularly move SpamCop Mail to TBird local folders, use Mozbackup for TBird/FFox to backup the local data, Ghost image the system main drive, and perform file x file backups, all external drives that I rotate and store in physically separate areas. It all takes about an hour a week, and (up until now) gives a warm feeling of data security.
Unfortunately, my MozBackup prior to the SpamCop data loss (which will we all hope be undone today) was already three days old when the SpamCop loss occurred; thus, a conundrum. MozBackup restores are not additive. Mail received in between is lost. And, in my case personally, in exactly that time period I had to take up leadership on a project, and am faced with not knowing what to do about the (possibly) important messages received in the meantime by multiple vendors and customers. Not something I planned, but there it is. Restore from Mozbackup and attempt to contact everyone asking them to resend? And, what would happen to the mail I restore to the SpamCop servers when (as I expected would happen within a day, not more than a week), SpamCop itself performs a restore; no, I thought, best to let the professionals perform the restore (and here we are a week later....).
Now I'll have to habituate regular downloads off the SpamCop servers, and not rely on the SpamCop server for persistent storage, unless SpamCop announces some reassuring new data security policies. I can live with it, but it's far from optimal.
Bottom line, DIY periodic backups still leave the period after the backup where your data is in limbo, and DIY restores risk overwriting or complicating the service provider restores (for that data you trusted to them). What's the answer? DIY backups every day? Twice a day mornign and evening? Every ten minutes?