Bicycle Quarterly often rides a bike for months to figure out what does and doesn't work and shake loose anything not on tight. Their reviews can sometimes seem harsh and nit-picky but they'll acknowledge that most of the bikes they choose for review are well designed, well made and often expensive to begin with so they hold them to a higher standard.
After riding it awhile they also change out the OEM tires that are usually cheaper to meet a price point and replace them with better tires that often allows a bike's performance to improve. Tires are often the first thing to wear out and get replaced so it more closely matches a user's ownership experience.