You're absolutely right, this kind of business with refurbished business laptops is quite common worldwide. While affordability and durability are key advantages, ensuring the security of these devices remains a crucial consideration for me.
Easy: wipe them and install whatever Linux distribution you prefer. I'd never use any pre-installed operating system, and prefer to buy my laptops empty.
Side question, how long do these refurbished devices last? It obviously cannot last as long as a brand-new device, which means it will fall apart sooner, is that not the case?
Can I answer with "forever"?
I've had new laptops break within a few years, sometimes mechanical (the hinges), sometimes the mainboard just giving up. I also have laptops 8-12 years old, and they get useless because of old age, not because they're breaking. Amazingly, most laptop batteries are still working after 10 years, although they run out quicker. And I do replace the CPU fan once in a while.
Another thing to check: power consumption. The less, the better. It's quiet, saves money, attracts less dust and stays colder. Whenever I buy a laptop, I first search the "TDP" for the CPU. The lower the better.
I have a refurbished Dell Latitude E6440 now since at least 2017 and it still works like a charm. When I purchased it I could barely see any signs of usage, lucky me. The battery that came with the laptop is still quite OK. To preserve battery life and when I don't need the battery when I can run the laptop on a power cord, I usually disconnect the battery when it is charged around 40%. On a Latitude you could also configure the battery management to only charge the battery to 50% max. when you're always plugged to the power cord. Such low charging levels are beneficial for battery life and endurance. I treat my laptops also always with some care and don't bang them around.
I never remove my laptop battery, and after 8 years it's at 70%. If I'd disconnect it, I can't use it when I need it (for instance when I unplug the laptop).