You're welcome, Jens!
Regarding the upgrade: If what you have is working correctly (and if you don't need to obtain technical support), there is no need to upgrade. There are some cases where we need to implement specific fixes and workarounds for certain versions of guest OSes, but if you don't hit any of those situations you'll be fine. If you do encounter problems, you might need to hack around to get things working, or maybe a newer version of Workstation would help – you could make use of the 30-day free trial to find out (but back up your VMs before trying it!).
Cheers,
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Darius