You will have to keep changing it as you move relays. All old posts will have your old nprofiles and thus link to your old relays. But apps should be smart enough to track relay hint changes and only use the latest ones.  

 Yeah, but if I put my  nprofile in an article, or someone mentinos me, 5 years later its not useful, or am i not understanding this correctly? 

 They need to update your relay when creating the nprofile. Apps shouldn't just blindly copy-paste the address without checking if the your/your post is still there.