Is it permissible to remain in a state of major ritual impurity (janabah) for a long time without performing ghusl, for no necessity, and is it permissible to leave the house or sleep in this state?

It is permissible to delay the ghusl of janabah (ritual impurity) until the time of prayer, because its obligation is not immediate but rather extended, as indicated by the hadiths. It is permissible for a person in a state of janabah to sleep before performing ghusl, and it is recommended for him to perform wudu (ablution) before sleeping. The Prophet, peace and blessings be upon him, used to perform wudu when he wanted to sleep or eat while in a state of janabah, and the command to perform wudu for a person in a state of janabah who wishes to sleep is for recommendation. As for the hadith: "Indeed, the angels do not enter a house in which there is a dog or a person in a state of janabah," it is weak, and even if it were authentic, what is meant by it is the one who is negligent in performing ghusl, not one who merely delays it with the intention of performing it later.