I change my oil once per year. In my '71 (which sees very few miles), I change the full flow filter annually, and the by-pass every 2-3 years. Amsoil also has a written guarentee, if you're worried about engine damage. Becoming a dealer or preferred customer makes getting oil pretty quick, too....

 

wow...I usually use fram..I wonder why soaring thinks it's bad

 

Read this study.
http://minimopar.knizefamily.net/oilfilterstudy.html