Ohoh! I figured something out!!!
Simply type an asterisk * into the search box on your order history page.
This will literally bring up everything you've ever ordered.
EDIT: It seems pretty easy to just go to each page of the order history and middle click the order details button to open a new tab, then click the tab, Ctrl-S to save as HTML. This is in Firefox by the way. The page titles have the order number, so it will stay somewhat organized. The benefit to doing it this way is that the links to the items will still work as long as newegg keeps those old pages up. I can still pull up the page for a K7S5A I bought in 2001 and all the pictures and specs are there... but it's so old there is no name on the product! 😀
Holy crap. I found the invoice for my red Icemat 2 mousepad which I'm still using constantly after 13 years!!!
Also just discovered something after many years of using Windows 10... it apparently has numerical sorting enabled, without needing leading zeros? Like, all of the files with long order numbers are in the correct order even though the oldest ones have fewer digits. I don't know how I've never noticed this before, but my mind is blown. I've always just manually added leading zeros when sorting files for the past 20+ years.
Now for some blitting from the back buffer.