7 years.

A beginner's guide to the Latin language, part 1. In a world that was better governed than the one in which we are forced to dwell, Latin was the foundation of the educational system, and the fountain of literacy: to know how to read and write was to know how to read and write Latin.  Knowing Latin, you could speak to anyone else who had been educated under the same régime.  Knowledge of the Latin language remains a matter worth pursuing. For speakers of English, Latin offers more than most others of the valuable intellectual exercise that comes from the study of foreign languages.  It opens a door to the classical, mediæval, and renaissance worlds.  The Latin language has a solemn beauty and cultural resonance that few others share.  It enhances your appreciation of the greatest music written in Europe.  In this article, which your interest or lack of same may turn into a series of several, we consider the grammatical structure of Latin and how it contrasts with English. [kuro5hin.org]

7 years. I had Latin in school for 7 years. It was the first foreign language I learned. English is actually only my third language. Considering that, it's absolutely ridiculous what's left of it in my head. I can, however typically get the gist of most of what's written on the walls in old churches throughout Europe. I absolutely love Renaissance arts, the early and high periods of the Italian Renaissance specifically and some of the greatest works are, unsurprisingly, in churches.

The above is indeed absolutely accurate, the referenced article contains a few things I don't agree with, though. For instance, last time I looked there were Roman languages, Indo-Germanic languages and Slavic languages as the biggest language groups in Europe.  Add Greek, and the unlikely group of Finnish and Hungarian, which share common roots, and with the exception of a few local languages that are entirely different, this should cover most of the language roots in Europe. "Indo-European" doesn't exist, though. English, German, Dutch, Norwegian, Swedish, Danish have all Indo-Germanic roots, while French, Italian and Spanish have Roman roots. So, historically speaking, our languages are either Imperialist or Barbarian.