Most roof leaks we see in Brooklyn and Queens don't come from the middle of the roof. They come from the edges and the joints: flashing around a chimney, a vent boot that's cracked, the seam where your roof meets the house next door. Those are repairs, and a good repair can buy many more years.
A replacement starts to make sense when the problem is the whole surface, not one spot. Shingles curling or missing in several areas, granules collecting in the gutters, soft spots when you walk the roof, or a flat roof with blisters and standing water across it are signs the roof itself is worn out.
Age matters too. An asphalt shingle roof past twenty years, or a flat roof that's been patched over and over, usually costs more to keep repairing than to replace. Every repair on a failing roof is a bet that the next leak won't show up somewhere else.
The best time to find out is before winter. Ice and snow turn small leaks into big ones, and emergency repairs in January are harder and more expensive than planned work in the fall. A free inspection gives you photos, a straight answer, and time to decide.