Suggestion;
Upon running the trainer, have an entry somewhere for the user to enter in a username and password. This of course will be the username and pass to a VALID unlimited membership account. If validated, have it save something on the PC somewhere so that the trainer can be run on this PC indefinitely without an online check.
This way, you still get your check, and you can validate the rightful owner (ie, check the encrypted information vs the actual username and pass, if the info entered is NOT matching then the trainer will not run).
Unfortunately, that would not solve the problem. One could still give out his/her credentials with the trainer. Ofc., eventually he/she would be banned, but, too late by than... However, if the trainer needs reauth. every day... ohh, right, no, the resetting the clock problem still persists...