What are you doing in each session, in terms of exercises, sets, and reps? The more info you lay out, the better feedback you can get.
As it stands, without knowing more details, if you wanted to prioritize your chest, you could tweak your plan to something like:
Mon - Chest, shoulders
Tues - Legs
Thurs - Chest, tris
Fri - Back, bis
Or check John Romaniello's article on specialization routines:
No kiddin'. I'd agree that higher frequency is more beneficial when training for size, but at the end of the day, it comes down to what you've found to best work for you. In your seven years of putzing around and presumably trying different types of programs, what type/frequency of training have you noticed delivered the best results?
How long have you been "a lot more serious"? In the past six months, how much bodyweight have you gained? How much has your strength increased on the basic lifts?