I do this too.
Even with my bf, I mean, he's MY BF, so it not like i have to go hunting for treasure. And yet I save mundane things like a lighter he gave me when I had forgotten mine, long after the gas is finished...
Also, I know its not me being sentimental, the thought process is different... Sentiment is "that's so sweet I'd like to hold onto this memory"....
While this is more "I want to absorb as much of you as possible"
So yes, guilty as charged.
I do try not to though, I eventually threw away the empty lighter.