You may or may not need 4 pressing days per week. Right now I'm only pressing 1 day with rotating rep ranges and my press is climbing for the first time in a year. I went from working sets with 165lbs to 180lbs only getting in 15is reps per week. I would only add more pressing slots if you've stagnated with what your currently working with. Don't just jump to 4 days without having worked towards it.