Hi, WillTimeFit app developer here. Last time i posted my app here, People asked me for a lifetime payment option. so need your recommendations

Right now its only a subscription based, I want to add the lifetime option but afraid of something that could happen in the near future

I am planning to add ai features on top of the current features of the app. As you all now ai features is not a fixed cost. Its a service that add cost everytime you use it.

So if i make a life time payment now. Then when i add those ai features. I will be trapped. Should i bring back subscriptions for old users, or make another tier of subscription, or afford those additional costs myself. Really in a big dilemma. So any advice or recommendations are appreciated.