I had a repair to address severe mitral stenosis in 2002. Since then I have had moderate mitral regurgitation and moderate mitral stenosis. I get an echo and have a cardiologist consult annually to monitor the valve area and ejection fraction, and yes they look for enlargement and take measurements. A couple times they've switched two every six months or done a TEE when they were concerned about the results, but so far those mini scares have confirmed things are still ok.
My left atrium is severely enlarged but they don't seem to mind that. My understanding is they are looking for left ventricle enlargement as a sign to do additional tests and consider surgery, even in the absence of symptoms. One of my husband's employees stopped going to annual appointments a few years after mitral repair; she did get that ventricular enlargement and that damage to the ventricle was not reversible or treatable. So it is important to keep up with those screenings.