Going back years?
I've got a spreadsheet that I started keeping in 2008. A tab each year for the kids, and another for the rest of the family.
At first it helped me budget.
Then it helped me avoid buying duplicate gifts - or keeping track of which book in a series I might get someone if they'd enjoyed the one the previous year I'd given them.
Now, as my kids are 24 and 20, it is a bit nostalgic to look back at what I bought them back in 2008 onwards. What little things they were into in the various years.
A bit sad too, when people are no longer on the list for gifts after a certain year.