Well, you will never know why it was refurbished in the first place. So there is always a bit of risk.
Many refurbished laptops come from businesses. This means daily 8-10 hours of use. Fans and hard drives tend to fail easily. Others are customer returns, for any reason. Damaged product re-paired, (new screens, keyboards, drives, fans). Or they'll just take a whole bunch of non-working systems, strip them for working parts, and build a complete system.
Keep in mind they are trying to maximize their return, so they will cut corners whenever possible.