Visible failure
Sagging runs, separated corners, rust, cracks, loose hangers, and gutters pulling away from the fascia are common replacement signals.
Water around the house
Overflow, soil erosion, stained siding, basement moisture, and pooling near walkways can all point to a gutter or downspout problem.
Get the whole system checked
A local installer should look at gutters, downspouts, roof edges, fascia, and where water exits around the home.