I had a Gameboy and Gameboy Advance, I don't remember the battery life being that long... That said, having to constantly buy batteries was the worst thing ever, so I'll gladly take a smaller battery life for something I can charge with a charger. I just wished the Switch charger was longer, so I could play it comfortably on the couch while it's charging.
The fact that I can't remember the battery life of the Gameboy makes it all the more irrelevant to me. Who plays for 8 hours straight anyway?
Ever heard of rechargeable batteries? No need to buy new batteries.
The Switch is compatible with USB-C cables, so buy a longer cable or an extension.