uncluttering one day and one thing at a time

It depends on what info you have in the notebooks and whether you think you need any of it. Most of my college notebooks just went into the recycling bin at university, because after the final, I didn't need them. Some of them had useful information that I copied into other places or kept a few pages and scanned, then recycled the notebooks. If you have a notebook that's entirely composed of useful info that you'll refer to later, keep it.