The answer is: 2 years

Acts 19:8,10 - Paul spent two years in the school at Tyrannus. He also spent 3 months in the synagogue at Ephesus. Acts 20:31 says three years in Ephesus, so he may have spent longer there, or rounded up a part year to a whole year. It was at least 2 years 3 months he spent in Ephesus.

During that vibrant time in Ephesus, Paul really poured his heart into his ministry. Set within the bustling cultural melting pot that boasts one of the Seven Wonders of the Ancient World— the Temple of Artemis— Ephesus served as a strategic hub for the spread of early Christianity. When he gathered in the school of Tyrannus, it seemed the perfect place for teaching since it likely functioned as a scholar haven by day, while Paul commandeered it for preaching during the quieter afternoons. Imagine him passionately conveying messages about grace and community to eager listeners, who might have represented diverse backgrounds.

Speaking of trivia, this two-year stint isn't just a tick on the timeline of Paul’s movements—it's where so many major themes in his letters were forged. Remember, Ephesus was also the home of the future Pauline epistle “Ephesians," focusing on unity, relationships, and the inclusivity of faith. Isn’t it fascinating that such impactful ideas were fostered within those walls? Members of the local and visiting populace would have sat in on these dynamic sessions, forming a nascent Christian community that was vibrant and perhaps a little bit rowdy!

By the time he left, he might’ve rounded things up to earn that estimated "three years" total, which, whether precise or ambiguous, left Ephesus smarter, more connected, and deeply influenced by Christ’s message through Paul—a legacy felt even today.