. . . It's going to take awhile for Greyhound to retire almost 2000 buses, though.
Until the hot dog salesman took over the company and ruined it, Greyhound traditionally sold coaches that had been in the fleet ten years or more in the fall, after the summer peak season. That usually was around 10% of the fleet, thus the overall fleet age would be about five years.
After several bankruptcies and numerous owner changes, who knows what their policy is today. . .
FWIW & HTH. . .