The peeps operate on a more-or-less 24-hour cycle. If you can only play in the evenings, you would probably benefit from switching the day/night cycles so that the peeps are in their daytime hours and have more energy. Once it gets to be evening in the game, they tend to be lower in energy as they follow their normal daily rhythms.

Many people have reported that they have several games going simultaneously in two or more player slots, so that they can experiment with a style of play and day/night cycles that works well for them.