I've been using Dauntless since the days when it was a one man show (Adrian. the founder, was a CFI and a graduate student at Yale, IIRC).
A few years ago I needed to add something to my CFI where I had taken the written ~10 years ago, but it had expired. An email to them and I had the codes for the latest version. Great service, good product and lifetime actually means lifetime.
That said, I'm sure Sheppard is good too.