DTW is the accumulator of DAL. Strong corporate presence to maintain a robust schedule. Has flights and fleets based there to cover almost all DAL destinations. While ATL/NYC are semi full with capacity, DTW remains underutilized so can grow and cover any issues in those hubs. During weather events many pax are routed through DTW (read makes nonreving a bit frustrating). Excellent airport facilities, historically the CPO is well run and mostly helpful since the merger. Of course no fleet is ever safe at DAL, but I’d feel confident that if you have 30 years to fly DTW should be a base. Size and flying always subject to change.

Best of luck with your choice.