One year:
https://www.mangago.zone/read-manga/love_gym/
Since elementary school:
https://www.mangago.zone/read-manga/yowamushi_danshi_renai_hajimemasu/
Unknown, but at least a month maybe?
https://www.mangago.zone/read-manga/viewfinder_ez/
these might be a BIT different than what you asked for, but i think it counts as tops with a phd in yearning
https://www.mangago.zone/read-manga/otsukaresamakurose_kun/
https://www.mangago.zone/read-manga/count_tachibana/
https://www.mangago.zone/read-manga/antidote_harusari/ (translations up to ch53 on another website)
https://www.mangago.zone/read-manga/paljae/
https://www.mangago.zone/read-manga/living_with_him/
https://www.mangago.zone/read-manga/the_deepest_confession/
ohhh thank you sm!!!! ヾ(❀╹◡╹)ﾉ~
thank youuuu!! ヾ(☆▽☆)
could anyone recommend me some bls where the top is a professional yearner that has been in love with the bottom for weeks/months/years??? plsss i love a pathetic man that struggles to talk to his crush (づ￣ ³￣)づ