Winters here are cold enough that metal contracts, and track brackets installed on homes from that 1999 wave of construction contract enough over a hard freeze to pull a track screw loose at the wall plate. Once one bracket loosens, the track flexes every time the door runs, and a flexing track is what actually throws rollers off the rail - it's rarely the roller's fault first.
The other common cause on newer double doors is simple: a car bumper or a bike handlebar catches the bottom bracket on a wide door, and because these doors are heavier than the narrower single-car doors common on older stock, the impact travels further up the track before it stops. We also see rollers that have gone brittle - not from age exactly, but from years of cold mornings where the plastic gets stiff and chips rather than rolls smoothly.
What we don't see much of here is rust-through track, which is common in wetter climates. Summerfield's cold-but-moderate winters mean the steel itself tends to outlast the brackets holding it to the frame.