Oil Change Question?

Hi All,
I have a question on oil changes on a car that I put @ 500 -700 miles a year on. A little background, the car is my 72 Demon 340, I use Valvoline VR1 10/30 racing oil with a Wix filter. I change the oil and filter once a year at the beginning of show season. Some people are telling me that is over kill and I should only have to change it every two years. I look at it as cheap insurance. Any opinions would be greatly appreciated.

Tom