"It appears to me from reading these sutta above that the practice must be renewed or refreshed with each arising of dukkha. Through impermanence and anatta there is no way to establish a constant unbound self, rather the unbinding and nibbana is a way out once found, but it is not constant, even for the Buddha?"
I think this is the main difference between the Buddha versus us: He has perfect and total control over his mental factors. The conceit of I, mine, and myself have been eradicated and so there's no need for Him to "renew the practice" every time for it has become second nature. For un-enlightened beings, we still have to make conscious efforts every moment because the "self" has not been transcended, "anatta" has not been penetrated. For every painful feeling that arises, we still have to make a conscious effort to see that there's no self. To the Buddha and His arhant disciples, it's all second nature for them. The physical pain is still there because the five aggregates are still there, but there's no Sidharta Gautama to suffer..