Is it OK to provide In App purchase in a free android app?

Is it possible(or OK) to provide in-app purchase in a free android app? I want to create one app that will be free for a limited time. User will be prompted to pay for it after few months. My app has lot 开发者_运维百科of user generated data. Migrating the data to a paid version is quite complicated.

If you're telling your users that this will be your demo version which will expire after a few months and then they'll have to purchase the full (paid) version, then I think its okay.

Its all about user experience, you know.

Users shouldn't feel cheated after downloading you app.

Giving a free app and once it becomes crucial for the user, you start asking for charges, will be quite evil.

I think you can hang on to the free app and use a key in the paid version, which unlocks the free app for continuous use. This technique is used in the app Cardio Trainer, but in their case they unlock other features of the free app.

You can absolutely have in-app purchase to upgrade. I have done it myself. But how do you stop them clearing the data or uninstall and re-install to get the free trial again?

I made mine have a number of free levels, and when they are complete it takes them to a shop.

However, I since added a Full Version to market along side this, and sales of that are massive compared to in-app purchase upgrades. I guess people trust bying from Market, and are not happy spending within the app.

So, you can do it, but I will in future continue with the free demo and full version separate apps. Also, in-app is a bit of a nightmare to implement compared to standard market licence checking.