This. Each person is different and as a 1500/5k runner I had many long runs of 12-16 miles but ultimately it’s a question of mechanics, quality, and frequency. Do you have a 7 day cycle, 10 day, or always 6+1off? Do you have any recurring injuries or niggles that will eventually become exacerbated (particularly if you lack or ignore proper strength or core routines, which haven’t been mentioned here and many runners slack on).
If you’re doing everything right no big deal, but as stated the vast majority of runners aren’t getting major benefits (that outweigh injury risk) beyond 90 minutes. Some athletes benefit far more from additional cross training or things like ~50-70 minute marathon pace tempos on the treadmill (to lower overall impact while keeping turnover high and keep them fresh for track sessions).
finally, you did 3 5k’s in a row, your body is likely also benefiting from learning how to suffer through the pain of the race and to some even unconscious degree your strategy (especially on the same course) May be improving finally. None of us are your coach so the litany of factors that are important here we can’t know and you would be, I will be direct here, foolish to attribute your sudden success merely to long runs.
I’m glad you’re seeing a breakthrough but be careful on how you interpret these results and responses here because as always, running is always ready to throw you a curveball. Def recommend working on mobility, core and strength as always though, increasing training like this makes it ever more important. Best of luck.