Currently the trial period extension is under Windows 10 not required, but you can continue to use the slmgr -rearm even with Windows 10!
The command slmgr -rearm is actually provided, even if the hardware has been not replaced on the PC to enable reactivation with a new product key (Key). Thus, you have an additional three times, new 30 days for the new activation.
For example with a new Windows-10 product key.
See also: ► Product Key in Windows 10 ► change the Admin User in Windows 10 ► Disable Password in Windows 10 ||
FAQ 75: Updated on: May 8th 2017 13:02