Around a year and 3 months after he ghosted me. Though more than just a romantic interest, he was also a childhood friend. So if you add the time in which he was supposedly also in agreement to keep the friendship afloat, a bit over 4 years.
Wish I could say it was a type of process, but it wasn't. I knew I had to move on when he ghosted me, though I still had some hope he may answer sooner or later. Though when his reaction to me sending a "Thank you for all the memories" message I prepared for my friends and university acquaintances when graduation came by, was to block me in all social media... it flipped a switch. I'm quick to sour on people, so I erased* all things related to him from my phone, and personal space. Sure, he comes to mind from time to time, but more than anything, it is as a remembrance of his hipocrisy and lies. He tried to do a balancing act his whole life, and at the end elected the side he said he hated. So if that is the route he wanted to take and he wasn't man enough to tell me face to face... well good luck in your life.
* As in throw into the deepest parts of my phone's contacts, messages and gallery. I like to keep record of everything, so I never actually delete anything from my phone or computer.