Below is straight from the Amsoil website. A friend of mine has been using the stuff for about 12 years, has over 200K on his Ford truck and over 150K on his wifes volvo and they still run like new. I've had no problems i.e. oil consumption, odd motor noise etc...
Normal Service(3) – Up to 25,000 miles or one year, whichever comes first.
Severe Service(4) – Up to 15,000 miles or one year, whichever comes first.
Replace AMSOIL Ea full-flow oil filter at the time of oil change up to 25,000 miles or one year service life, whichever comes first (other brands at standard OEM* intervals).