Measured from their first listed coaching job on Wikipedia, years it took the last 10 first-time CFB championship coaches to win it all:

Ryan Day: 22
Jim Harbaugh: 29
Kirby Smart: 22
Ed Orgeron: 35
Dabo Swinney: 23
Jimbo Fisher: 25
Gene Chizik: 24
Les Miles: 27
Urban Meyer: 21
Mack Brown: 32