The 33-year-old former Porto boss took over at Stamford Bridge in June. Buck told BBC Sport: "We do envy Arsene Wenger at Arsenal and Sir Alex Ferguson at Manchester United in terms of longevity, but it shouldn't be longevity for longevity's sake.
"It has to be the right guy in the job for 10 or 15 years and, in light of Andre's age, he may well be that guy." Buck added: "Everyone thinks his age might have been a negative but it's a positive."
Wenger, 61, is celebrating 15 years at Arsenal since his appointment in 1996. Ferguson, 69, arrived at Manchester United a decade earlier and, in November, will mark 25 years as manager at Old Trafford.