Bucky doesn't mind the laugh, he wishes he could bottle hers and keep it in his pocket for a rainy day.

"Awhile..." he admits with a soft huff of a laugh. "A... really long while..." he chuckles, brushing his nose against hers. "Definitely since before the serum..." That seems important to distinguish. It wasn't something that he'd only felt when she became the definition of peak human condition, it was older than that.