From my perspective, the forms or chi sau can never be practiced too much, and I would distinctly not advocate minimizing time or emphasis on these. However, I agree that it is entirely possible and generally the case that too little time will be spent on anything or even everything … forms, chi sau, application analysis and practice, gor sau, sparring/fighting*, etc..
*[Terms applied loosely and dangerously.]
Time is the single most important and constraining resource for all of us. Therefore, and I think most of us will agree, appropriate balance is of highest consideration. However, “splitting the time evenly” or in some fixed proportions may not provide the optimum balance, and immediate needs do not remain constant. IMHO, without minimally “enough” time in the sets and chi sau on an ongoing basis, the remainder of work will never fulfill its potential and may even supplant the essence of Wing Chun with something unnecessarily superficial. I also believe that the optimal proportion of time on forms vs. chi sau vs. other activities will vary throughout the stages of a given practitioner’s development.
From my own personal experience, application work continuously informs me where my errors are, where my skills are weakest, and why I need much, much more time in the forms and chi sau work. It is an iterative and integrated process. Forms training and chi sau are my primary training vehicles, not merely "reference dictionaries,” supplemental exercises, or time wasted going through some motions. They are the meat and potatoes of my Wing Chun. These are where my Wing Chun capabilities are built; to forgo or foreshorten time spent in forms and chi sau is for me to be pennywise and pound foolish, and ultimately cheats me of excellence in the application realm.
If we look at those who excelled before us, and also at those who failed to meet their potential, what patterns can we observe? Our data sets and perspectives on this will of course differ. My own teacher has been an avid Wing Chun practitioner for over 40 years, and even he still learns and improves through daily practice of the sets and chi sau. I think it is fair to say that most who touch his hands would agree he does okay.
Of course my perspective is colored by the view of Wing Chun as a lifetime process of deep development rather than a quick fix.
Regards,