Lead nurturing is the steady follow-up that keeps a lead engaged from first contact until they are ready to buy or sell, which for open house leads can be months. It is a mix of timely first contact and a longer sequence of useful touches.
Open houses produce a lot of early-stage leads, so nurturing is where most of the eventual value is captured. The first same-day touch starts it; a real nurture sequence, run in your CRM, is what carries the lead the rest of the way.