The area's housing runs from 1938 up to 2013, with a median around 1986 across the wider service territory - but Summertown's own median lands closer to 1993, meaning its doors cluster into a narrower window than Columbia's older core. That matters because hardware ages in generations, not years: a 1993 door is now at the point where torsion springs, rated for a set number of cycles, are reaching or past the end of that rating, all at roughly the same time across the neighborhood. We don't see this spread evenly in a town with houses from six different decades. Here, it's concentrated, which is exactly why a maintenance pass now catches several doors at the same stage of wear instead of one outlier.