Hi folks:
There was a post in the ESXi 5 discussion group about Windows 10 VMs unexpectedly crashing after about 24 hours. I've found that this is also a problem with ESXi 6 as my Windows 10 VM appeared to simply shutdown within 24 hours or so of me starting them, which I had at first attributed to some sort of activation issue. If you are having this issue see this thread for information on the cause and a workaround until a patch to correct the problem is released:
https://communities.vmware.com/message/2533457#2533457