15 years for 1B/tx/s, 35 years for 1M/tx/s. Or more generally: t_years = doubling_time*(txid_bits - log( initial_tx_rate_per_year * doubling_time / log(2)

15 years for 1B/tx/s, 35 years for 1M/tx/s. Or more generally: t_years = doubling_time*(txid_bits - log( initial_tx_rate_per_year * doubling_time / log(2)) / log(2))