There is no doubt that this means that if he is not sacked eventually, he'll end up coaching too long, but geez, lets make that call at the end of a season not 5 games in. As OSM says, he coached a team to the prelim final last season, basically never misses finals for the last 35 years, and a few months ago got England within a converted try winning the World Cup.
You can say the same about, for example, the QLD State of origin team. At some stage the likes of Smith, Slater, GI, JT & Cronk will play 1 season too long if they don't retire. But you know what? They've built up so many credits that they deserve to be kept until they've played too long, because if you make that call too early you risk missing out on some very productive years. It would have been so easy after 2014 to say they've been there too long, had their run and it's time to replace them, but then we probably wouldn't have the 3 in a row from 2015 (and counting).