Almost every roof call we get starts the same way: a stain on a ceiling, or a neighbor who just had their roof done and mentioned that yours looks old. Neither one tells you whether you need a repair or a replacement, and the difference between those two numbers is large enough to be worth twenty minutes of honest inspection.
The first thing we do is get on the roof, and the second is get in the attic. From above we're looking at granule loss, cupping or curling at the shingle edges, cracked pipe boots, and the condition of the valleys and the flashing where the roof meets a chimney or a wall. From below, in the attic, we're looking for daylight, damp sheathing, rusted nail tips, and stained rafters. Attic staining tells you where water has been going for months, which is usually a very different place from where it eventually dripped onto your ceiling.
A repair is the right call when the roof field is still in good shape and the problem is a specific detail: one bad boot, a lifted valley, flashing that pulled away from a sidewall, or a dozen shingles a storm took off. Those are real fixes, not stopgaps, and a good repair on a healthy roof buys years.
A replacement is the right call when the failure is spread across the field rather than concentrated in one spot: widespread granule loss, brittle shingles that crack when you lift them, or a second layer already on the house. It's also the call when the decking underneath has gone soft, because no amount of shingle work fixes rotten sheathing.
One Georgia-specific note: our summer heat ages a roof from the inside as much as from the sky. An attic that isn't venting properly bakes the underside of the deck and shortens shingle life significantly. When we replace a roof, sizing the ridge and soffit venting to the attic volume is part of the job, not an upsell. Getting that right is often the difference between a roof that makes it to the end of its rating and one that doesn't.