I did something similar to this for my husband a few years ago, and I can relate to your labor of love. And yet it’s well worth every bit of effort.
Mine wasn’t little notes. I started a Google doc on January 1 of that year and decided I’d write down something each day that made me thankful for our lives together. I wrote funny things and painful things. I didn’t sugarcoat the bad days, but always finished them with the reminder of how thankful I was that I had him to go through the bad days with.
I couldn’t believe how many pages it turned out to be when December 31 rolled around. But it was well worth it, and every so often I go through the file myself to read and remember.