If you have replaced the phone at least three times, actually walk into a store and explain the situation to a store manager. Remain calm and go in with an actual goal in mind but make sure that (1) your expectations are realistic and (2) you are prepared to put up a fight in the event Verizon isn't willing to give into your demands right away.
Document every service call you make, every issue you encounter with the device and track the number of replacements (both phone and accessory) you have to make due to owning and operating a faulty product. Let them know that rather than being able to use a device that you signed a two-year agreement for and will be paying $2,000 towards (device and service contract) you are stuck with a paperweight. Let them know that you (1) need a working phone, regardless of model and (2) if you aren't going to be provided with a working device to serve out your two year contract you will be filing a formal complaint with the BBB.
They will likely ask that you accept one more HTC Droid Eris CPO device a final time in order to resolve the issue. They may even comp you an accessory like a case or a charger for your troubles. Tell them at this point that your faith in the brand is shaken and that you would just much rather move on to another device that either falls into the smartphone or feature phone category. Be firm - you signed the contract and have thus far fulfilled your end of the bargain by being a paying customer. (Right?)
In many cases, the store will first attempt to replicate the problems you are having with the device while you are there with them. In many cases, some bugs just cannot be done at will. It then becomes a matter of "do I want this replacement done under my Employee ID"...sad to say but true. Store employees, CSR's on the phone and store managers all have their own individual credit and compensation limits. Internal reports are produced that can determine how much credit a Verizon employee extends to a customer, how often they do it and more. When I worked in wireless years ago that sort of reporting was just in its infancy; I can only imagine how it has evolved over time now.
If you do not get satisfactory resolution in the store, try over the phone. If that doesn't work, try again. Try up to three times before hitting the BBB button and getting them involved.
Most importantly - during any dispute with a carrier, whether it is billing or otherwise, continue to pay the standard monthly charges and do not let your account fall in poor standing unless it is unavoidable as it is with billing issues. Verizon, the BBB or any other consumer group will not help you if you are a deadbeat and do not pay your bill.
And on a final note - don't expect something for nothing. If the price of an Incredible exceeds (and it will) the price you paid for the Droid Eris with subsidy, offer to pay the difference. You will not get a free Incredible for bitching to high heaven. That is not how it works. Verizon is a business, they are in it to make money.