Couldn't find this posted already. The End realm 100% respawns from scratch every time it is entered. New dragon fight, all altered - broken or placed.
Edit: Not sure if in both single and multiplayer, but this is happening on my server
Comments 6
Is this still a concern in the current Minecraft version? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases. If this has been done, we can reopen the issue.
Keep in mind that the "Resolved"-Status on this ticket just means "Answered", and that we are waiting for further information on whether this issue still exists or not. We will reopen it as soon as the requested information has been delivered.
if you have a bukkit or a server with any plugins it could be doing that.