Out of experience with 2 large services. Can't share stats, sorry. It may seem unlikely, but it's true :) I'm talking average, many take up to 6 months. Now you know why there are so many ads for crappy services online :) ps: I didn't say "at least", I said "on average".
The math of subscription services generally goes like this: acquiring a paying customer is going to cost you about 15-60$ each (for typical lifestyle services). So lifetime value needs to be more than that. Once you're live, you tweak those numbers, make acquisition more efficient and increase lifetime value.
