I can't speak of other Crypto-currencies with same enthusiasts and confidence but with Bitcoin I don't set any time horizon not even 10 years plus because the idea don't make any sense.
When you are buy and steadily accumulating Bitcoin why are you then setting a time frame, do you at any point intend to quit Bitcoin and convert all your asset to Fiat?
Bitcoin is not just passing by to stop at a given time so I am not setting a time frame for it.

Bitcoin is part of my savings, I try to get Bitcoin steadily and keep accumulating and if I need something and can't source other means I can convert and solve my problems but I save in Bitcoin steadily, doing this consistently you will see how far you can grow. I have accepted that Bitcoin is here to stay so no plan of ever converting Bitcoin to Fiat completely.