I have a lot of dark brown in my artwork designed in photoshop, which is C73-M62-Y98-K73. Does it matter that the sum is over 300%? Should I be limiting my colours to a certain percentage?
What you are referring to is called TAC or Total Area Coverage; it is usually defined by your printer. 300% is a good personal limit, as many range from around 240 to 320. If it is personal work it is completely down to your judgement.