I am so happy to learn other people use a spreadsheet to track their purses, Coach and otherwise. I just started doing it this year after I discovered vintage/older Coach leather bags. I had originally planned to buy one only, but then it took on a life of it's own... I find it useful to track usage, which is one metric I use to justify the purchase after the fact.
After learning so much on purse forum, especially the authenticate and rehab threads, I am more diligent about cleaning and conditioning the bags - so I track that, too.