Limit the aborts is even worse, now is about punish players that can spend more time playing, and those that developed a strategy
Player that is online 10 minutes, cannot expect to compete with someone that is 4 hrs online.
Player online 4hr, cannot expect to compete with the one that does 8hrs.
Player online 4hr can compete with 8hr if develops a much better game strategy.
This is true for EVERY GAME that exists: more time = higher level; better strategy = higher level.
BE CAREFUL: the only thing that DIAMONDS do in this game, is save up TIME, accelerating the city development, everything is obtainable without diamonds in the long time run.
DO something that forces players to go offline by blocking their gameplay, whats the point of using diamonds if they still have to wait for next day now.
Have you consider a "time off" as better option?
Like after 1 hr of cycling quests have a 5min block?
this sounds even healthy for those doing endless hours: go blink your eyes a few minutes and stretch the fingers before starting over,