Here's an example of a trainee schedule (one that goes to school as well). Note: I do not know if this is an actual trainee scheldule you will face, this is what I gather from research.

Training Scheldule

6:00 - 7:00 Get up and ready/ Commute to School

7:00 - 3:00 School (if you didn't live in Korea before this, most likely it would be a school near your dorm or an international school)

3:00 - 6:00 Training 

6:00 - 7:00 Dinner/Break (Maybe you won't have a dinner break in some cases and will just eat in the training room)

7:00 - 12:00 Training

12:00 - 2:00 Possible Homework

2:00 - 6:00 Sleep

Of course, each entertainment agency will have their different training scheldule. Not only that, but you might be classified early on as different types of trainees (ones that just arrived, ones that have been staying in the company for quite some time, and ones that are preparing to debut). In this case, the trainess that are preparing to debut will have the most intense scheldule versus those who have just arrived in the entertainment. Also, it can be possible that personal responsibility will play a major role in how long you train. As if you want to quickly debut and improve, you might train much longer that let's say a 9 or 10 year old who isn't in a hurry to debut. 

If you aren't going to school, then you will be pretty much training all day. Lay from EXO who didn't go to school when he started training, trained about 12-13 hours everyday.

Also, these are approximate times, as I don't know which schools you might be going to or what your own personal training scheldule will be. But this gives you a rough estimate on how much time you will be spending training and it seems like a good 8 hours.

If you are willing to do this everyday for 2-4 years, then I believe you have the proper mindset of a Kpop trainee.