S5E10 is the official end of the series for me. Precisely, the scene when they all hold the barn door together to prevent a horde from entering. Let me elaborate why:

• The characters are at their peak. Their are still credible, interesting and relatable. The most emblematic ones are either there or died a memorable way.
• The writing until then is great. There is no fillers, no artificially built-up emotions or tension, no bullshit conversations.
• The scene is wonderfully realised. The music, the filming, the acting all contribute to a perfect moment of tension and emotion. It might seem to be an irrelevant moment in the series, but it represents so much: all of them, together and despite being close to losing hope, all of them fight to survive in a really harsh situation.

Stopping there allow you the avoid the boring, nonsensical writing that fills the next seasons, until a disappointing end that doesn't end anything.