You are looking at repentance through the lens of salvation by works. Repentance is an attitude, not an action in response to wrongdoing. That attitude carries through senility because it resides in the soul in the keeping of the Holy Spirit. This is why the truly saved do not simply sin to their heart's content despite being dead to sin in God's eyes through Christ crucified. Your only alternative to that is a perpetual prison of sin and repentance which is a silly idea. I mean, what if you sinned and a meteor immediately struck you before you could repent? Do you go to Hell despite Christ crucified, and your acceptance of him as Lord?