I signed up for the life time after I'd had a few too may one night, seemed like really good value at the time.
I'd have to use Brewers Friend for 10 years or so to make it worth it and to be honest I've not stuck with any other brewing software for 10 years yet so it remains to be seen if it was good value. Having said that I do like how Brewers Friend is all laid out and I find it easy to use so it's not looking too bad.