Just as a data point, I've sold one-time-purchase desktop software for a few years and refunds have been pretty few and far between.

I understand the fear that a bunch of people will buy it and immediately request a refund because what's to stop them! but that hasn't been my experience, and I think having a generous refund policy engenders some good will and leads to more sales.

(of course if you've actually had problems with this, disregard! :)

To address the GP's comment though - I don't know the legalities behind this, but I remember buying physical software, in boxes, from stores, where the policy was "once you open the box/break the plastic seal you can't return it" and in the digital realm it seems like downloading would be the closest proxy to that. I just think concerns about this sort of dishonesty are pretty overblown, especially on the scale of indie software.