You can also export to DNG. That may be a more "archival" standard.
That is what ADOBE is dreaming of, DNG as archival format. Until such time it is yet another raw (or cooked) format and little or no gain to be achieved when converting. Even ADOBE themselves advice to keep the original (raw) file for archiving purposes.
Do a save metadata first of that is not already automatically done, then export your keeprs of a shoot to a folder on a drive.
The seems to be aposibility to export to DVD from within Lightroom, however i have no experience with it.
Personally what i do, looks like the oher way around compare to your approach. From a given shoot after the selection of keepers and rejects is done, i move all rejects to a different folder; main reason is to reduce the cluttering in my keepers folder.
The folder with the keepers , the rejects folder and the folder holding any derived images is grouped together in a parent folder. In this way all images of a shoot are kept in one "shoot" structure. Note that I have a habit of not throwing(deleting) away rejects unless absolutely worthless. In the parent folder i also have a folder for administrative files, such as assignment, lists, instructions, etc.
I use collections to further collect keepers into groupings/collections for whatever given purpose.
I also use metadata and keywords to allow searching, retrieving and grouping.
I use the cataloging capabilites of LR as my asset management system for all my images, and it forms the core element of my system that supports my workflow from "klick" to the "kick" of presenting the images.
I have a backup solution that on a regular basis automatically backups my images and my catalog.
Next to my "working copy" images and catalog the backup procedure realises 4 backup copies, spread over different disks and computers. ( is am still working on an off-site backup).
The cost is not a limiting factor, it requires a software program and some set of harddisks. DVD's are fine when the amount in GByte is relatively small, even then it is relatively costly compared to usb-harddisks, and you still face the issue how to store them (it is rather bulky compared to harddiks) and how to assure that in case of emergency (a fire or a flood) you can quickly take them with you as one set(not leaving any image behind).
Also i find recovering images from a DVD takes a lot of time.