Been following this thread and I must say, while it sucks, at least Livernois is working on it. The OP's story is almost identical to mine, except that the company was MMR and I waited until the third failure. Unfortunately for me, the first two valve failures took out cylinders. MMR rebuilt the engine (not originally built by them), but after the third failure, I sent the engine to RGR for inspection. As you can imagine, things were found to be wrong. I wrote MMR a letter and got a call from Mark. After some discussion, he opted to replace the engine with an MMR 1000 long block built to my specs and warrantied to produce it's advertised power. We both washed our hands of the head issues and I had JPC/RGR build my stage 3 heads and design my cam.
A lot of people (including myself) have had a lot of bad things to say about MMR, but I've been thinking a lot about this.
It seems every time this happens with a company, it's during a period of growth. Usually, the company has an established reputation and when things go wrong, people shrug it off at first. If things keep happening, it gets to where it is with MMR, and now Livernois.
In just about every industry, I've seen companies struggle with growth. I'm a government contractor and have been in three companies that saw more growth than than they could handle at the time. Each time, customers were really, really pissed off.
Companies seem to vary with how they handle this growth, as only someone with significant business experience can understand how to best prepare for this. A lot of that also depends on available capital. You need to invest capital before you can truly handle growth, and that takes guts, as if you overestimate your growth, you could be out an investment.
FWIW, the only Mustang vendor I've seen handle growth well has been JPC. Much of that has been because Justin stays so engaged on so many levels of business. Of course, that has to take a personal toll as well.
The past few years have taught me a lot. Most importantly, it is to stop whatever discussion is happening and address the larger problem. I think the OP did that, but others may have just bowed out and never given the company a chance to make it right. Just as Mark at MMR changed got involved and helped with me with my issue, Mike at Livernois seems to be doing the same. I think the customers and companies learn a lot due to these issues that they wouldn't if the customer doesn't doesn't give them a chance to fix them.
At any rate, that's my piece. I still have a knot in my gut when I think about firing up the new engine for the first time, but I already know I've been through the worst and survived. Here's hoping the OP, myself, and others get through this kinda shit.