I think a lot of the naysayers here are forgetting that "breaking in" a boar brush is really "controlled damage" to the hairs. You're trying to get hair to split and fray in a predictable fashion, not use alchemic rituals to transmute one kind of hair into another. Why, exactly, must a good brush be earned after already paying for it? Now, I agree that a certain level of care should be used, and one should consider the possible side-effects of the chosen treatment. I personally would not freeze the brush, leave it completely submerged, or take sandpaper to the tips. I have tried the hot water and while there are some concerns with that it saved my 49 Pro from becoming trash.
I'm not saying that there's anything wrong with wanting it to mature over time, I'm just saying that it's not unreasonable for some of us to want the performance we payed for.
I'm not saying that there's anything wrong with wanting it to mature over time, I'm just saying that it's not unreasonable for some of us to want the performance we payed for.