Most games have learned that players respond better to incentives than penalties, even when they are mathematically equivalent. Instead of having a hunger debuff, food provides a buff, and all the content is balanced with the assumption that you are using food buffs. One World of Warcraft design included a bonus to XP when you started playing, decaying to neutral and then a penalty over time; this was changed to a Well Rested buff that does exactly the same thing, where playing without the buff means earning XP at the old penalty rate.
The latter is an example of the common incentive to play periodically for a moderate amount of time rather than trying to go from level 1 to the cap in one massive binge. Playing in moderation is better for your health, the game’s community, and the long term health of the game. Examples of systems that support this are daily rewards and bonuses that accumulate during offline time like the xp bonus in WoW or LotRO or the explicit “offline time” in A Tale in the Desert. The core idea here is providing a bonus the first time you do something today, which makes the first time very rewarding and creates an implicit penalty for farming.
The implementation of the Zen Garden in Plants vs. Zombies 2 is an interesting example. You have 6 to 12 flowerpots. You plant a sprout in each that gradually grows to become a boost. (“Gradually” means hours, although that can be shortened.) A boost gives that plant a large bonus for one round.
In practice, that means your first few rounds of play include at least one boosted plant. With some care, you could have a really awesome round in which every plant is boosted. You will crush that round and laugh in the zombies’ faces. And then you are back to normal. You re-plant your sprouts and either do something else or keep playing normally.
The Far Future world, introduced with the Zen Garden, seems to be balanced assuming you will be using some boosts. This both creates chances for highly skilled players to face greater challenges and provides more casual players with a boost to get past that.
Which is not to imply that casuals are unskilled, but we expect the hardcore to get better with all that time they spend. Being “hardcore” in Plants vs. Zombies is an atypical life decision.