This is highly variable from athlete to athlete, depending on their ability level and genetics.
The best in the world train with ridiculously high volume, and despite what dogmatic HIT advocates will tell you, they NEED to.
The best at Westside Barbell have as many training sessions as 14-30 a week. Louie Simmons, their coach, trains constantly all day. His sets are extremely high.
The Metal Militia are the best bench presses in the world, and they train their bench 2x a week, once for 3 hours and the other for 2 hours. They will literally do hundreds of sets split up between those two workouts.
The best Olympic Lifters in the world train with more volume then both of the previous groups I just mentioned.
Of course beginner and intermediate athletes cannot train with this much volume. They must start from much humbler beginnings.
Having said that, training the way you always have, will leave you with the body you've always already had. If you want to improve, all training variables must be increased. This includes frequencly, intensity, and volume. You can't increase intensity too much, and there is a limit to how much you can raise frequency. Soon your only option is to increase your volume.