Yes, holes typically fill in after aeration, but the time it takes for them to fill in can vary depending on several factors. The size of the holes created during aeration is generally small and shallow, typically around 2 to 3 inches deep, and they are created using specialized equipment like aeration machines. The removed soil plugs are left on the surface of the lawn to break down and help improve soil structure. After aeration, the holes created in the soil will eventually fill in as the surrounding soil settles back into the holes. This process can take anywhere from a few days to several weeks, depending on the type of soil, weather conditions, and the amount of foot traffic or use the area receives.