Deleting Old Versions of Cubase?

I have Cubase 6, 7, 7.5 on my drive (I’m using version 8 now). Can I safely delete these files off my drive or is there a reason to keep them?
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After every Cubase Upgrade I’ve eventually deleted the previous versions once I’m satisfied that the new version is working well.

Some users keep older versions for compatibility reasons (avoiding any unforeseen conflicts), like, when collaborating with other people who are using older Cubase versions.