The right time to move on

So I was watching Hi! My Sweetheart, a 2010 Taiwanese Drama, and one of the episode scene made me think for a bit. It was when Lee Wei character He Yan Feng asks Rainie Yang's character Chen Bao Zhu if its time to move on. What he ment was that, if it was time to let that person in her heart to move out so that another person could move in. This was because, she was in love with Show Luo's character Lin Da Lang (who was actually Xue Hai's fake name) for 3 years and its been 3 years since the break up and since she's been searching for him. That night she decides that Yan Feng was right and she decided to pack the Pink Panther and her only photo of her and Da Lang away in a box and to move on.

So what made me think was that it does take that long to move on from someone. I mean, if you have a crush on someone and realise they don't feel the same, does it take the same amount of time to stop having feelings for them? This is because I was in that kind of situation, in the past. It took me 6 months to fall for 'him', and 6 months to forget about 'him'. But in the end, I think it was a good thing that I didn't form a relationship with him because we have been such good friends.
Does this also apply for people who just been in a relationship and have broken up? Like if you been with someone for a year or 2, then will it take 1 or 2 years to mend your broken heart and get "back on the horse" or to move on/ forget about them?