I recently came back to bug heroes 2 and realize that the Heart System was recently implemented. My personal problems with it:
-50 Hearts is too low. The lowest amount I can use is 12 Hearts (2 Bugs, each costs 6) which means I can only play 50/12 ~= 4 times.
-Had to watch a lot of ads to keep my Hearts amount afloat.
-Waiting an hour for the Hearts amount to increase partially is quite boring.
-The game itself is grindy enough. The Heart system makes the progress even more frustrating.