2)chopping up the entry platform when you go to The End (this platform isn't always there, such as if you landed on the island proper). This platform will be regenerated if it's missing every time you return to The End and will even overwrite any blocks placed at minimum in the space taken up by the platform. I dunno if the area above and below the platform is also reserved, but a superstructure below would be a good way to save the drops.
3)resummoning the ender dragon using 4 ender crystals placed around the exit portal. This causes the obsidian towers with the ender crystals on top to reform. You can do this infinitely, but you only get up to 20 gateway portals.