Are these your items? Or your kid's items?
I try to be mindful of what I am saving and why. They why might change as time passes, so it's to re-evaluate here and there. I had a box of notes my friends and I passed in high school. I am sure I saved them to remember all the funny stories. But reading them 15 years later they read like gibberish. I had no idea what we were talking about. The notes were written to be hard to read to an outsider in case a teacher got them, which meant they made NO SENSE to me anymore. Maybe if I had re-read them yearly, but I did not. So, I tossed them all after sending some pictures to the friends involved (who I still count as my best friends).
So it's time to comb through the boxes. You don't need to get rid of 100%, but aim to get rid of at least half of it. There's very little stuff that the next generation wants. They might your favorite platter, or your favorite piece of art, but beyond that they don't want boxes of memorabilia that they didn't amass.