I tend to agree with that range of decline based on history.
70% to 80% is the range I think the next bear season will be regardless of how high the price goes this year. Of course it's not so much a certainty that we then describe it as doubt - but the cycle is almost always similar. I don't expect there to be a 90% drop from the ATH in the next bear season - if it does, that's a risk that long-term investors need to consider and they need to be prepared with a backup plan.
In respect to what I already said before, I do have that thought too that bitcoin price will drawdown to -60% or -70% during the bear season which no body can accurately know what will happen. At this point where the government of some countries are showing interest in adoption of bitcoin for federal reserve, ETF approval, and some money people (just as Phil'ma called it) showing so much interest on bitcoin, we might likely not see a huge price plunge during the bear season.