Yeah. I was shocked when I totalled up all I'd spent at DAZ. Was more than enough to buy a full size Prius.
I originally had a column in my spreadsheets that specified the type of product ... Figure (characters/clothing related), Architectural (buildings, vehicles, furniture), and Nature (landscapes, plants, weather). I had also categorized the zips by Year, Type (Figure, Architectural, Nature), and then Order No. I generally have an inkling on a product name, which then gets me to the product in my spreadsheet. From there, it's easy to find the zip since the Purchase Date and Order No are right there.
I also separate products in my runtimes by type. For example, if it's an architectural building, I use folders named Bridge and Pier, Castle and Keep, Courtyard, Crypt and Graveyard, Futuristic, Garden and Bower, Interior, Pavilion, Ruins, Steeple and Tower, Temple, Town and Country (which is along the lines of villages and city type products). If I don't know a name, I generally remember whether it's a castle or a crypt or a garden structure (like Fantasy Gazebo) ... and so on. That will get me to the product name, which then takes me back to the spreadsheet to see where the zip is located.
It does get to be a pain keeping the spreadsheet updated though. Even if it's mostly copy and paste from the order.