Solution to avoid sudden cancelation

lots of UK series are great and have few episodes.

Why american show MUST have 867 episodes?

In case a show does not get the expeceted ratings, why can t they just make a final episode to wrap it up, like they did in Jericho?

Well, the solution mentioned is, while shooting the first episodes, take the chance and shoot an alternate sequence that could become a mini series in case they decide to cancel. Very little extra money would be spent, and it would be well spent as the show could even be sold overseas as it would become a mini series instead of a total failure.

The writing should also predict the chance of cancelation.

I guess I must a total genius for thinking it, or the opposite!