Just something I have idly wondered about over the years. Suppose somebody gives you a gift, and while you appreciate it, for various reasons you just don't get around to using it for a long time, like years. For me it's usually books. I'm a really slow reader, I have a lot of books, and I have to be in the right mood to read something, so I have books I got as Christmas or birthday presents literally years ago that I haven't read yet, but I fully intend to and look forward to.
When I finally read one, I always wonder if I should mention it to the giver, as one does--"Hey, that book you got me? I really liked it!" On the one hand, they might enjoy knowing their gift was used and appreciated. On the other hand, some people realize I took a long time to get around to it and get... offended is too strong a word, but more like an eye roll and "Didn't I give that to you years ago?" It's one thing if they've been waiting for me to say something about it, but a lot of the time, the giver has totally forgotten about the gift until I bring it up.
It's a bit like, should you send a thank-you card for something, even if it's really late? On the one hand, you should send a thank-you card. On the other, it also reminds the person just how late the card is, when (if they're like me) they might have forgotten they sent you anything or just fuzzily assumed you sent thanks already.