I have heard that bass voices tend to continue deepening well after puberty, sometimes into the early thirties. Is this true? I believe Geoff Castellucci once said in an interview that at eighteen he was proud that he could hit an E2, but now he sings the occasional F#1. Is he purely an anomaly, or is he an extreme example of a typical phenomenon?
For a quick follow-up to this, as an eighteen-year-old low baritone who can reach a D2 fairly consistently, is it reasonable to expect C2s and lower someday, or is this likely out of reach?