How slow would your times have to be(or have to have been) for you to quit running after HS/college?
myself
If I was much slower than 18min 5k in HS i would have quit then.
If I was slower than 16min 5k in college i would have quit then.
i was just on the cusp of seriously quitting in both cases but managed to squeak by. (for better or worse)
I had similar hs pr's as you and after cross my senior year i decided to train more seriously and see if i could make my college team. If i hadn't progressesed at much as i did in that year (down to 16:30), i would not have run competitively.
If I hadn't been fast enough to make my D3 team then I might have quit then.
As far as continuing post-college, I don't think it's going to matter how fast I run during what's left of my college career, as I'm still not going to be anywhere near sub-elite status. If I feel like I want to keep running, then I will.