The channel has a doubling time of 260 days. Which means that as long as the bitcoins are inside you are doubling your money in 9 months. Except that if you buy when it is above, you might need to wait much more (max 465 days, so 1 year and 100 days), and if you are really really luck and clever you could make it in as short as 69 days.
Somehow the channel is bounded below by the actual needs of bitcoin . Which is growing exponentially. While above people are trying to invest in the price and buying and selling. It should be worth noting how Bitcoin mining reward halved on the august 2016. This diminished the . What probably happened is that the bitcoin economy was growing, and the number of bitcoin in circulation were also growing, but somehow the two were balanced. When the halvening occurred the quantity of money started not to grow enough respect to the growth of the economy, and the value of bitcoin shoot up. This would mean that when the halvening occurs again, bitcoin should look for a new channel.
Of course all this unless the technical limit does not stop it all. Suppose, for example, that every transaction start costing much more than visa, much more than any other mean of exchange, much more than dash, and so on. Then the growth might stop, and bitcoin will reach its level of saturation.
If this would happen we would see some other crytpocurrency pick up the exponential growth. Until the need for the whole world for crypto for exchange is saturated.