What’s the most I could realistically make from Qmee a month, given enough time and persistence?

I think Qmee is a great app, and I want to reap as much as I can from it while the app is still around. For anyone who has made at least 300 a month, how many hours a day do you spend on the app, whether it be desktop or phone? The most I made from Qmee in the shortest amount of time was $87. That took just about two weeks to achieve.