0-$1000: 8 years
This took closer to 4 years than 8 years.the adoption is like this and we are still in the "early adopters" stage which is pretty slow. and it will get faster soon and becomes vertical (with it price will be the same) until the mass adoption and then it plateaus.
Based on this graph, one could argue we're all Innovators! Less than 2.5% of the population uses Bitcoin. I have very high hopes for Bitcoin once SegWit is used a lot more, especially when the Lighting Network becomes main stream. As far as I understand it right now LN would mean I can create a "small expenses wallet" on LN, and put the equivalent of $100 in there. I can then use LN to send and receive small amounts (buy 2 coffee, sell one to a colleague). All off this off-chain with near instant confirmations and very low fees. That would allow Bitcoin to go mainstream. Faucets could instantly pay small amounts again too.Meanwhile, large transactions would remain on-chain. If my LN-wallet gets loaded, I can transfer some to any other wallet again.
So far for my future dreams. Back to this graph: note the S-shape that's common for market penetration. Exponential growth can't be sustained forever, at some point it will have to slow down.
All in all I see a bright future for Bitcoin. But do yourself a favour: don't compare a linear thing (time) with an exponential thing (price) without using a logarithmic scale.