the last one wasnt long ago believe me you cant do a game like this one with actual monthly upgrades because is a lot of work and little to none content per update so maybe every 6 months at least but it depends on the developer just wait because this where is the update thingy (not saying because of you but in general everyone asking for it) normally ends in the developer not giving an update anymore or just not quality upgrades, i can see he is putting a lot of effort in the game and im sure he is prioritizing quality over the speed