Slow recovery

I've struggled for weeks - since about Christmas - to get back out and run, but a stubborn case of Achilles tendonitis has held me back. My rehab over that time has been a mixture of rest, stretches, elipticals and walking. About once a week I have tried running, if you want to call it that, but each time I could tell I still had more healing to do.
That's not to say there hasn't been progress. When I started my weekly runs, I would walk a half mile and then jog a half. If I got three miles in before the pain got too bad, it was a good outing. It would take a full week for the inflammation to subside completely. Eventually, I reduced the walking to a quarter mile and increased the jog to three-quarters of a mile. I added another mile at some point, too. There'd be pain, but not as much. The recovery period dropped to 6 and then 5 days.
Over the last three weeks I've started doing easy sessions on the "dreadmill" at the gym. I'm very leery of that machine because I've suffered two or three significant injuries on it over the last few years. But I figured if I kept the pace very slow it would be OK. So far, so good.
I've progressed now on the treadmill to a walk/run split of .15/.85, and my 4 mile workout last night was 4 miles in 47:32. That's an 11:53 pace. I was tempted to go a little longer, but I could feel the discomfort building and decided to pull the plug. I was not stiff or sore afterward or even now, 12 hours later.
So, I'll continue these careful workouts and try to build from here. -- Rob