It's not as bad as it sounds, really.
Your notebooks are useful primarily because writing things down is a useful way to process ideas and your recent notes provide helpful context about where you left off. Reading your notes again far in the future is a much less common use. However, you don't know ahead of time which few of your notes you will ever need again. Storing your completed notebooks so you can find them later takes seconds; scanning every page of a notebook and uploading it to a service that can search your handwriting takes minutes, if you want to do that.
When you created your notebooks, you gave them names and volume numbers, and maybe categories. This gives you a way to refer to each page of each notebook completely uniquely:
A page's "full name" is category/topic/volume:page. You only need to write this entire "full name" when referring to a page in a notebook in a different category entirely, and when labeling the spine of the notebook when you first start using it. When you're referring to a page in the same category, but a different topic, use topic/volume:page; if you need a different notebook in the same topic, use volume:page, which is reasonably short to write as it's a simple pair of numbers.
Writing the name of your notebooks on the spine helps you follow these "links" in your notes, since you can match the notebook name to the reference in your notes. Your notebooks will be physically stored in a way that matches these names, so if you need to pull a notebook out of your archive, you should be able to find it quickly. Putting a notebook away requires finding its place alphabetically once, and then you are likely to never have to touch it again; if you do, then you needed something in it, so the effort of sorting your notebooks has already paid off when it let you find the note you wanted.
When you're done with a notebook, you should archive it - store it in a way that you can find it later. You can archive your notebooks digitally, physically, or both; it is by far best to do both, but if you're pressed for time, you can archive them only physically. Archiving your notebooks only digitally saves you very little time, since putting a notebook in a box in alphabetical order is only seconds slower than leaving it on your desk and then spilling coffee on it.
If you scan your notes, you can store them using software that can recognize your handwriting and search it later. There are at least four services that can do this:
All of these services can be used for free, with various limitations (usually total data stored, but Evernote instead limits you to a certain number of devices and a certain amount of data per month; you can work around this by using smaller or lower-quality images for your scans.) If you're scanning notebooks with stuff related to your job, check your employer's information security policies to verify that they permit use of the cloud platform you want to store your notes in - some employers have strict rules about where their intellectual property can be stored (and if you did it for money, it's their IP now).
To digitally archive a notebook, scan every page and upload it to one of these services. If you have a flatbed scanner, that is the fastest way to scan your notebook. If you don't, your smartphone camera will help; Evernote and OneNote have integrated features for taking pictures of paper documents and cleaning them up to look similar to a scan, and this built-in software is your best bet if you are using these as your archiving tools and don't have a flatbed scanner. If you aren't using Evernote or OneNote, or don't like their scanning tools, consider CamScanner for Android or ScanBot for iOS instead.
Since these services search your handwriting, you don't need to do any additional sorting or organization (although you can if you want). Some of these services can only identify handwriting in .jpg-format scans, not .pdf-format scans, which may affect how you use your scanning software.
Once you've finished scanning a filled notebook, it's time to put it away. This is what the archival box, with index tabs, is for.
To put a notebook away:
You have now physically archived your notebook.