In many cases it does change over time, but it doesn’t have to. The 2 biggest culprits of yellowing are direct sunlight and improper chemicals used to clean it. If your countertops get a lot of direct UV light, they can begin yellowing after only a year. The light breaks down the resins used to bind the quartz countertops together, resulting in that yellowing look. Light or white countertops are the most susceptible to the change.
Consider either putting in sun blockers in the windows or installing darker countertops. The other problem comes from using harsh chemicals to clean the countertops with. People using vinegar or bleach or anything like that are likely to see damage to their quartz countertops over time.
All you need is something mild (like a few drops of dish soap) and water. Though stain-resistant, you shouldn’t let anything sit on them for a long time (e.g. coffee, vinegar, wine, etc.). Along with this, make sure you always wipe up quickly after having fats or acidic foods on the countertops while cooking. These things can cause yellowing if they aren’t dealt with in a timely manner.