Hi,
Well, OP, in some respects you are better off than me at present. I don't have the external storage. But I plan to soon.
Currently I just burn two DVDs for backup. I plan to re-burn them every 5 or 6 years. One set is kept off-site. I store all RAW files, first, then all edited files (JPEGs, TIFFs, various sizes). I consider the original RAW to be the most important to keep.
When I set up an external arrangement, I want it to have hot-swappable drives. I'll use a mirror RAID, so everything is burned to two drives, rather than a JBOD. That's in case one fails. I'd never use striped RAID, since data gets split between drives and may be impossible to retrieve if one or the other fails.
By having a hot-swappable set up, I can have two sets of disks, one set of drives off site for storage, the other set in use and having automatic backups written to it, and swap them every week. That way in the event of a catastrophe that destroys the external backup, I would lose no more than a weeks work.
I use simple yyyy_mm_dd_xxxx file names.If it's a big day's shoot, I'll use the date of the shoot. If I'm downloading a small number of images off a card that were taken over a period of several days, I'll use the download date. It's close enough for my purposes.
Occasionally I'll tag a folder with a short suffix to identify a particular event in that folder, but I don't use that suffix on the files within it. Only with edited files, I may have simple suffixes on some, if there there are several versions of a particular one. That might be "a, b, c" or size like "5x7, 8x10, 11x14". And, I'll add an "s" behind a final version of an image that's been sharpened.
Accompanying the archive DVDs, I print out thumbnail catalogs. Maybe not all images, if there are a lot of similar ones, but a representative selection. In the case of a job, though, the catalog is usually all the final edited images.
Because my filing system is date-related, my backup DVDs are clearly marked with a date close to when they were first burned, so I will easily know when I should re-burn them in the future (or move the images to more stable storage media, should one come available). I don't have any that have come up for re-burning, yet, but I will within the next year or so.
Now, besides the fact that it's a long number series, I can think of one possible problem with using a date as a file name. Stock photographers might think twice, because it could shorten the "shelf life" of an image that's actually quite usable and salable. A file number that's so obviously the date the photo was taken (or close to it) is a give away that *might* lead potential buyers to skip over an "old" image, even though subject matter isn't dated in any way. I know one stock shooter who currently has all his camera's internal clocks set to 2026 for this reason. That way the buyer can't just check the EXIF and find out the date the shot was actually taken. I don't know how he keeps potential buyers from just checking the copyright registration, which presumably would be within a year or less of the date the image was shot.
You might want to look at "The DAM Book: Digital Asset Management for Photographers". It's available online... Just Google for it.