This is not a thread about if URL shortener are good or not, I'm just wondering how long such created TinyURL will be available? Is the given URL available "forever"?
If so - is there a way to override such URL again?
From their website:
Obviously subject to the service existing indefinitely!
By override, do you mean modify the redirection target URL? I can't readily see anywhere that this is stated, although I'm fairly sure it cannot be modified.