I spilled water on my laptop back in 2008. Fried the HD. I thought I'd lost not just my DS supplies (I'd only started like 6m prior), but also all of my digital photos, including DD's first year of life. That made me a bit of a fanatic lol. (I was able to recover the photos!)
I tag when I unzip, and I've made a rule that I have to buy/download/unzip all on the same day (or weekend, if it's a big sale). I also tag products via Metadata because you can't "lose" those tags, unlike ACDSee etc (hearing horror stories of lost tags--which also means lost time--made me too nervous to use those programs).
I also have an Excel spreadsheet with product name, designer, store, themes, colors, and Misc (retired, bundle, part of a series, etc). The themes section is where I write whatever tags I assigned the to product's folder image (I have a folder of these images, renamed to the kit name and designer initials). It's also a place to write more specific themes; instead of just "bday" I might type "sixteen" for a kit that has a lot of sixteenth-birthday stuff. So, I do all of this on the day of purchase. Every once in awhile I'll make a big purchase and this process maybe gets delayed for a week, but I try really hard not to let stuff sit. It doesn't hurt that I don't buy nearly as much as I used to.
The one thing I've been "bad" about lately is backing up onto my EHDs. I have backblaze, so its easy to say "everything's in the cloud. I can wait another week before backing up."
Anyway! I don't really mess with my system anymore. It took me a couple years to get it figured out, but I love it, and it works for me.
