And I also agree with the buy-and-hold technique, I think it can be also used in mining, even in the bear market, where people invest in miners, and holds the coins they got, so they could harvest in the bull market.
That could work if we're dealing with investors having an eye on the very long term, but most miners aren't like that because their bills come back every month. You could try to hold your coins for like a month or six, but there will be a breaking point where you stop holding them and start selling to cover your operation costs.
Bitcoin has been going down for over a year, and if you look at the price development, miners were better off unloading their coins before we broke $6000 than holding them, and while the odds of another severe correction is on the lower side, you can't take it for granted and have to sell to make sure that you can stay operational for at least a couple of more months would a correction take place.