Similar question to the OP. I am getting a used ThinkPad carbon i7 8gen , 16gb ram, 512ssd for 35k. Usecase is just ms word, powerpoint and Google sheets, very basic Excel files. Want it to last at least 3-4 years. New hp pavilion ryzen 5625u is available for 45k on Flipkart. My budget permits 45k too but would really prefer a busines machine like thinoad due to the build. Do you think the i7 8gen can last 4 years for a very basic productivity usecase.
The two main components prone to failure in used laptops are batteries (you'd certainly have to replace it after 3 years), and to a lesser extent, SSD. Depends how heavily its been used.
So check how much a replacement battery will cost, and check the SSD health (and do other diagnostics) before buying it.
The Thinkpad is a business class laptop, so most likely you will get faster SSD, better WiFi card, probably a better screen and a sturdy build.
So if diagnostics look okay, and you are getting the Thinkpad + a new battery at a similar or lower price than the new HP Pavilion - for sure, I'd pick the thinkpad.
Ryzen usually beats Intel on battery life, but the Thinkpad has an intel U processor and a larger battery than the HP and with a new battery, should last similar (or even more) than the Ryzen.
The Thinkpad is a no brainer for 1-2 years use. But because you said 4 years, that's trickier - but personally, I'd still inch towards the Thinkpad if it is in great condition and used under 3 years.