As a time management game, Operation Mania will have its slice of difficulties. Of course, difficulty is good if its spaced out evenly - which in this game, it is. The level progresses exponentially, getting more difficulty as the game goes on, in this manner, you don't get bored after a few stages because its just become too easy. Aside from the picking up, diagnosing and dropping off of patients, players will be given the chance to play the various mini-games that are connected with different types of surgeries involved.
This variation in game style gives players ample opportunity to stretch their attention span as they do not ultimately get bored of the repetitive actions in game.
Topping up, of course is regular for games like these, after each level, use the money you've earned to improve on your speed. That's always a good thing, faster time means more reasons to get patient.