I think the longer they can hang on, the more damage the tories can leave for Labour to repair. When the repair takes a longer time than the electorate, who like simplistic answers, can understand the tories will have a stick to beat the Labour government with. They're looking to return after 1 term,.
OTOH, I've seen it suggested that Labour still suffers some damage from memories (and myths) of the Winter of Discontent. I think that this current winter will be far more discontented than that of 40+ years ago (at least our public services worked better then, despite the strikes) and it's possible that similar folk memory would keep the tories out of office for a very long time.