There is great variation in hikers, but here’s some generalizations from my PCT. Of course these are just generalizations, and your mileage may vary…
Older hikers tend to hike slower and steadier. Fewer zero days, fewer high-mileage days, shorter town stays, fewer side trips. More focus on getting miles done every day. Generally tend to plan more as they hike, trying to hike as smart as possible, e.g. thinking ahead several days to line up for hot climbs in the morning. Older hikers tend to depend less on candy bars, and more often have their own home-made recipes. Older hikers have a wide variety of gear, some ultra-light, and others with a good share of classical gear. Some older hikers get in shape before the hike, some just start slow on the trail and build up. Older hikers tend to have a good tolerance for aches and pains, but also know exactly how far to push the body and when to slow down --that knowledge might be the most important point. Basically any older hiker in reasonable shape can hike quite successfully if they have determination, tenacity and a little luck.
Steady