I trained low volume HIT for some years. This january i went back to RIR Training with high volume and I gotta say I get pretty much the same results with high volume and not going to failure than with HIT. Problem for me with going to failure in every set is that I feel destroyed after. Its just not doable for me when working full time job, having a family, pets and soon to be a father. I get the same results with a lot more volume, higher frequency, staying at 1-2 RIR and feeling good after 1,5-2 hours in the gym and not like conplete dogshit. Not saying it is for everyone, hell no, I honestly wish I was made for lower volume, going to failure more often and so on but my body and my life just do not feel right with it. People just have to find out what works for them in their life. As always, its good to know science but its better to try it for yourself.