Will all disbelievers remain eternally in Hell, regardless of the length of their lives or the magnitude of their sins?

Every sin is forgiven by Allah except disbelief (kufr) and associating partners with Him (shirk). Whoever dies upon these will not be forgiven by Allah and will abide eternally in the Fire. This is based on the Almighty's saying: "Indeed, Allah does not forgive association with Him, but He forgives what is less than that for whom He wills," and the Almighty's saying: "Indeed, he who associates others with Allah - Allah has forbidden him Paradise, and his refuge will be the Fire." No soul will enter Paradise except a Muslim soul, by the consensus of Muslims. The inhabitants of Hell will vary in punishment according to their disbelief and injustice; it is not a single degree, and the hypocrites will be in the lowest depth of the Fire.