A lot of older fiction portrays wizards as immortal by default. No need for lichdom or anything else. Gandalf, for example, doesn't seem to age at all from the moment he appears in Middle-Earth, to the time of the Hobbit, and then through the 70-80 years to the Lord of the Rings. He's a wizard by race though, so it's a little different. He's not the only example though.
