If you are having troubling making sure your Sims bars do not drop too low, pause game play, then tell your Sims what they need to do. When you resume the game you will not have to worry about trying to get your Sims bars full.
Save the game, then enable the move_objects on code. Get your Sim to a nice open location. Go to Buy mode and delete your Sim. Go to Live mode and quickly pause game play to prevent it from going fast forward. Click on the person's face. It will have a red cross over it. The Sim will be in the middle of the house with full need bars, and some may still be recharging. The only problem is that most of the time it has only half of the Bladder bar.