You seem to be using a lot of colours unnecessarily. The lightest colour in the beard can be replaced by one of the skin tones, the lightest part of the glasses can be replaced with the lightest skin tone, many colours in the hair are near repeats (both of other hair shades, and of skin tones), etc. Also, the colouring is starting to get a bit pillowy, mainly due to the abundance of shades and amount of AA you're using. Limited AA can be used to great effect, as can a small palette, when properly applied.
Overall, though, lots of this comes down to personal preference. High colour count, for example, isn't necessarily bad; it's up to you. I really love these lines, too, and I'm sure the finished piece'll look fantastic. Keep it up
