If the bull market recur periodically, like what happened in late 2017, how long dose a cycle would take? It seems at least longer than a year now..
If we're going to look at the historical logs, bull run seems to occur every 2 years. But its not a good estimates as we all know that past performances doesn't mean future success in this market.
But if you look at the next possible bull run which is 2020, we will be having the next "bitcoin halving" that may trigger the a bull run. I'm sure that the demand will increase as bitcoin will be scarce and limited so everyone will want to get their hands on that "precious" bitcoins.