A new technology doubles its performance every 2 years, starting at 10 while the old plateau sits at 80. Set the slider to the years until crossover.

6 (answers within ±0.5 count)

Three doublings: $10 \rightarrow 20 \rightarrow 40 \rightarrow 80$ in 6 years. An 8× performance gap sounds unassailable and is three doublings from gone, the arithmetic every incumbent should run before laughing at a toy.