Mentor did bit dirty move lately, as the "perpetual" licenses now mean "we will send you new activation keys each year to each few years for the lastest version you paid mainentance for, even if you are not on active subscription anymore", and all the license keys have build in timeout now. This applies both to nodelocked and mobile compute (USB dongle key). I was not happy to find out either.
IMO, this is done to prevent any licenses trasfers out of control of official distribution channels, but is the most harsh way I had seen implemented by anyone by far.