I usually move the files in the dcbackup into a new folder labelled according to the file I installed right away. So, if I install the greenhouse, then I select all the files in the dcbackup (minus the ccmerged file) and cut and paste them into a new folder I've named greenhouse. Then, I install something else and do that again. This keeps all the sets backup files in nice, organized folders.
Those backup files are all just numbers and therefore almost impossible to tell which content they actually match. I feel they aren't needed; but sometimes when you upload a lot or a sim, your computer might check here before including the content in your upload. I've tested this and had content upload that had no files in the dcbackup (because I deleted or moved them from there after installing). I feel it's only required for third party cc to transfer. BUT, I'm not on the last patch and every system is different, so... you can keep all the backup files organized or just a big hodge podge or delete or move them at your discretion.