The mistake I made with Specter was letting myself get talked into pursuing a voice cast before I was ready. People committed but were then told to wait, in some cases for months, before I was ready to move forward. By the time I was ready to actually proceed, some people had simply dropped out. It's frustrating, and from my perspective, I've gotten as far with Specter as I ever planned to--anything else is just a bonus.
If I wasn't so eager to get started on Retribution, I might be willing to invest a little more time and effort into Specter, but as it is, making Specter taught me a lot and I'm very eager to put that to use with Retribution.
I may still at some future time go back and add in the VO's that I already have. We will see.