[AlexandrBel]

I regularly keep in touch with some clients, but they are unlikely to tell you how to get people to buy a subscription :)

[sublinear]

I think they meant to say you should directly ask those customers why they didn't buy a subscription.

[j45]

Many will tell you what they think it's worth, and if the app went away (even with lifetime), what they would be willing to pay elsewhere.

Asking lifetime customers may not provide a full picture though.