Should you be worried if your boyfriend keeps letters from past relationships?

well i wuld be kinda worried and curious about it because hes only keeping them to look over Tha past and remember what he used to have and if he was over whatever girls hes saving those letters from he wuldnt have them but he never got rid of them so hes obviously still into those girls or he misses them so hes keeping tha notes or letters but i wuld be worried..