I've definitely turned a corner on this now. All throughout the winter, I kept losing the adjustment within a week, or two at the most. My AO doc sent me to a specialist in craniosacral massage. This treatment didn't seem particularly effective in increasing the hold time (which increased by about a week), but it definitely decreased general tension and stress in my head/neck. This also seemed to help my TMJ/jaw movement (abnormal translation upon opening my mouth is pretty much gone now). The frequency of these massages was about once a week at first, and has since decreased to about once a month (may try for every six weeks in the near future).
Once I started to suspect scalene involvement (due to some self trigger point work), my doc sent me to a PT who does soft tissue work with the Graston Technique. This is a method that uses metal instruments to break up fascial adhesions and scar tissue. The PT did this on my scalenes, levator scapulae, and a few other neck and shoulder muscles. This work seemed to really be the key in helping me to hold the adjustment. After a couple of sessions of Graston, I was holding for more than a month (until I had a bicycle wipeout and lost it).
Now, I've been holding for about 3 months without the need for an atlas adjustment. My AO doc has still felt the need to do some adjustments with the activator on my thoracic spine and pelvis. This, along with some scapular retraction exercises, has helped a lot with my primary symptom (the constant back cracking and tension).
Needless to say, my doc and I are both very pleased at this new found progress. She still thinks that my foot pronation is contributing to my pelvic issues, but after reading Steven's excellent article
(w/fs), I've stuck to my guns on not getting her recommended orthotics. Although she still hates the idea of me wearing Fivefingers, she's softened a bit on her position that orthotics are required for my case, given the progress I've made.
I'm looking forward to continue healing and strengthening after years (decades?) of chronic problems. My frequency of posting here will probably decrease unless something changes drastically, although I do plan to do a much fuller write-up of my full end-to-end experience in the hope that it's informative to someone else in a similar situation down the line. These will probably take the form of blogs posts that I'll link here. In the meantime, if anybody has any questions, I'll try to answer them as honestly and completely as I'm able to.