All in all, it would seem that the entire Star Fox chronology, at least as it was presented from Star Fox 64 to Star Fox Command, spans roughly 20 years.

Star Fox 64's whole backstory take place across 10 years, beginning with Andross' banishment to Venom and then James' death/betrayal on Venom five years later, and the events of Star Fox 64 taking place another five years later after that. The Japan-only "Farewell Beloved Falco" Manga, the canonical manga follow up to Star Fox 64 and prelude to Star Fox Adventures, would take place four years later, and SFA would take place another four years later after that. Star Fox Assault takes place one year after the events of SFA, and Star Fox Command was said to take place a vague 2-3 years after the events of Assault. This would amount to overall roughly 21-22 years.