Interesting thread. I've had bursitis on back of heel for more than a year along with slight achilles pain, but have trained through it. I suppose everyone's different, but stretching, NSAIDs, self massaging, and slight heel lifts have always kept me training/racing without the injury getting any worse, and often it's not even noticeable.
Also, I do take 1-3 weeks off between training cycles (fall/spring marathons), so this may keep the achilles healthy enough. I'm not suggesting you train through it--particularly if it hurts enough to cause a limp or inability to run normally. But I do think that it is possible for some people to continue running the same as always as long as they tend to the problem.