i honestly think this premium system is fine compared to other systems, but still not really the best. lions and research are awarded at a decent enough pace, and tier II (and some tier I) planes are fun enough and accessible in only about 1-3 days of gameplay. you get a decent amount of premium points to start with as well. at the very least, premium currency is not needed for progression at a decent pace (where it seems like the player is getting somewhere with the work they put in), which is the number one requirement i have for a passing free-to-play model