If you hide the files in other files theat is used by other programs like windiws and in directoris like C:\Windows\Temp\ The user won`t notace a thing in the most recent edited files and windows have hard to detect the hiding among the files.
You can altsoe make it soe theat if you have tryed to tamper with any files the information is deleted and replaced with random bytes, Theat will lead to the user have to pay the monthly valute again.
You can conect to an internet user to get time by using the NET TIME wich uses another machine to syncronice waches. The user gets hes clock reset at the same time.
Information is then at its weak point in transfer from the host to the user.
But to overcome theat make the program ask an ip adress theat is given from the host and cheack theat the information is right. It is still posible to tamper with but regarding the safty on other programs you need a clever man to tamper with this.
The man will tamper to give the tamper information open to all users but You just change code with the monthly information.