Undertaker NEVER had "go away heat". He may have gotten some over the last 5 years or so if he was out there every week. However, the man (with a few exceptions) basically wrestled once a year for the better part of the last decade.
He had a couple of "stinkers" in that time period, but came back better the next time out and gave us a hell of a performance in what was considered to be his last match (though in cinematic form). The cinematic approach left people wanting more (from him) and not some of the crap they produced in cinematic form after WM 36. But, he decided (we think) to hang up the hat and jacket for good.