Jethro66, your motivations sound similar to mine. I am slabbing my most collectible books so that I can (hopefully) realize as much of their full value as possible when the time comes to sell. I had a billing issue with CGC in which CGC was not responsive that I have, so far, elected not to pursue with BBB because I don't believe (in my case) the catch is worth the chase. But I have reviewed the BBB page for CGC, and I agree with you that most of the posters there realized movement on their issues. You've made a good faith effort with CGC to resolve your issues, CGC HAS NOT MADE a good faith effort to respond, and it is probably very appropriate for you to contact BBB to raise the profile of your issue.
Also, like you, I intend to hold my books for some time and don't need quick turnaround (or turnaround much earlier than stated TAT). CGC offers Modern and Economy tiers for a stated fee which includes customer service. They should support these tiers without the payment of add-on fees.