What makes electrolysis or electroplating take so long ? What stage takes longer when ions are attracted to electrodes or when they gain or lose electrons at electrode. And if we are talking about an electrolyte composed of positive ions and electrons , which is faster, electrons entering the circuit at positive electrode or gaining electrons by positive ions at negative electrode?
It depends: The rate of electrolysis is limited either by the electric source or by the ion concentration. I am inexperienced with electrolysis but I imagine that quality may increase as the the process slows, much like crystals grow with more imperfections when the rate of crystallization is fast.
There is no such thing as an electrolyte solution composed of positive ions and electrons.
"Activity coefficients of single ions cannot be measured experimentally because an electrolyte solution must contain both positively charged ions and negatively charged ions." -Debye–Hückel theory
Electroplating systems tend to use an electrode source that replenishes the solvent ions plated onto the target electrode.