The better part of five years. My very first roleplaying experience was in a basement at the hands of a bunch of middle aged men, playing Earthdawn in 1994 at the tender age of 7.

Nobody gave a shit beyond making the obvious allowances to the kid, just once every fortnight my uncle kidnapped me and we'd all go play pretend for as many hours as I could sit around for. In hindsight nobody cared wether I was there or not, but they showed me how it worked, filled me in on whatever I'd missed (usually a session or two) and gave me tips on how to play that seem obvious today.

"A bunch of middle aged men kept me in a basement for hours and taught me to 'roleplay'" normally ends with "and that's how I got molested" but it was one of the best gaming experiences in my life to date.