Good, Cheap and Fast has driven 1,080 sales this year; only 9 of those items have been returned. That's a sub-1% return rate and I'm very proud of it.
Last year, I decided not to use Google Analytics on the site: https://www.goodcheapandfast.com/articles/what-i-measure
Instead, I chose to focus on Amazon's affiliate analytics. It was a questionable decision, but I think it was the right one.