There is not unlimited and, worse, it is not possible to delete them permanently, at least I dont't know the method to do so. Jetmouse can only hide the subscriptions (GTM 25 and 35 that has exactly the same receiver and use the same firmware). I have in hand a GTM 25 with maximum possible subscriptions recorded (should be around 30 with 3.10 fw), but I can not to install anything extra. Actually I install but when I reset the GPS and receiver it disappears, indicating that it was not recorded in non-volatile memory.