Once you make it past about level 50 you have to use many of your boosters to pass the levels in a timely fashion. It takes 30 minutes to recover 1 life so if you run out your done for a while unless you want to spend coins, if you have them. But of course you can buy things with real money to help with all the above issues, too bad I refuse to spend money on a mobile game. It also takes several stars to buy each improvement for the house which is all I am interested in, it just takes too long.