Monetize with a premise that user will leave eventually

It's a bit unfortunate downside of my project, but I suppose all dating services does suffer from a similar problem. Once the user finds the match they don't need an app to continue paying for it.

To be honest, I don't mind that much. Money is not my primary motivation, but I already know that there will be some expenses involved with running such service so I need to cover for those and ideally get something extra so I can work on improving the service.

The monthly subscription model is probably the worst approach as an uncertain revenue flow. Paying per year only could make more sense but feels kinda forced. And since dating apps need many users, it might drive away some of them who don't want to pay a bigger sum right of the bat.

Since my app is sort of like a "phone", I am seriously toying with the idea of a virtual wallet where each call will use up some of the money. Such an approach would be the best toward covering running costs and it will scale up with the number of users nicely. And setting up automatic recharge when running low, users won't need to bother with it.

Additionally, I am thinking about combining that with onetime payment for lifetime access. It would be a higher sum, but cheaper in the long run. Does that make sense for a dating app where people know they will eventually stop using it?

Any other approach that comes to your mind?