I read a fic a few months ago on AO3, where Brian and Justin still had sex that night, but then Justin left and he DID end up going to Dartmouth, and about once a year they would just randomly run into each other. I think Justin was double majoring in business and art. Regardless, at one point, they actually PLANNED to meet somewhere either in the Caribbean or maybe South America? But Brian found out about his cancer, and stayed behind, not letting Justin know, but Jennifer (Who I think was acting as Brian's real estate agent for Kinnetik and had no idea about her son and Brian's meetings) helped him during that time. Justin started thinking it was bad luck to actually plan their meetings and letting it be sporadic was key.
This fic was incomplete on AO3, but this page has shown me magical ways of finding complete fics, so not only do I hope it's found, but also I hope there's a complete version somewhere out there! You all are amazing and magical! Thank you for the help!
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Thank you, Eurekaone! “Same Time, Next Year” by Cheburashka2 — Fic can be found here: https://archiveofourown.org/works/1238515/chapters/2543062