I say, enjoy the hookups. See what happens. Heartbreak is part of life, and you never know what will happen in the future. Maybe you’ll meet someone really great and it won’t be such a heartbreak when he goes to college. Not every goodbye is forever and maybe you can just pause the relationship and continue it some future time.
Do keep yourself in check, though. Maybe give yourself a little space when you need it, and don’t devote your social calendar to just him.
Don’t borrow worries and be sad all summer. Have fun.