How many versions of an APP are kept installed

Question

I was looking at how apps are stored in windows 8, as a means to understand how things flow in your deployment of apps, and found that you store versions of our apps.

How many versions do you store? Is it only 2 like clickonce ? or more?

Here is a screen shot of 2 versions of some apps stored on my //build/ tablet

http://www.flickr.com/photos/onlyawesomestuff/6947140093/

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