I wouldn't. Its important to keep the electrons in it moving. If you leave it at 100% charge for a week it will freeze your electrons. Apple does not recommend leaving your portable plugged in all the time.
If you dont plan on using your iPhone for more than three weeks, Apple recommends that you store it with the battery charged between 50%-75% and the device completely turned off, not just put to sleep. If you store it when the battery is fully discharged, it could fall into a deep discharge state, which renders it incapable of holding any charge. Conversely, if you store it fully charged for an extended period of time, the battery may experience some loss of battery capacity, meaning it will have a shorter life.