1 Peter 5:1

The elders; men commissioned to have the care of churches and to preach the gospel, but with a distinct allusion to the fact that they were also literally elders in respect to age. 1 Peter 5:5 Who am also an elder; his higher office of apostle included the lower office of elder, which latter he here applies to himself, because he wishes to exhort as an equal, not to command as an apostle: compare Philemon 1:8-9

Those who have long, faithfully, and successfully preached the gospel, are best fitted to exhort others rightly to do it.