If "they" run out of ETN from millions of people using this Mobile Miner (I personally don't think this will happen), then the mined ETN's would still hypothetically be on the market, like bitcoin when all the bitcoins are mined, the mined bitcoins would still be on the market, (if there still is a planet with humans, computers & the internet left at that point)... =)

But I am not a "financial expert" or even a "crypto expert" or "professional fortuneteller",
I am just a guy who is interested in cryptos, so maybe you are right? Please go and read their: https://electroneum.com/overview-white-paper.pdf ...

Mining Electroneum coins from your phone
Installing the free Electroneum app (Apple or Android) immediately gives the user the ability to start gaining Electroneum in their wallet. All the time the app is live (even
in background mode) it will be running the unique
app based crypto
mining experience,
which requires ZERO technical knowledge.
It takes up very little bandwidth, so doesn’t cost much to run on 3G or 4G data.
We’ve made the money supply of
Electroneum coins high, to enable our app users to quickly gain
some Electroneum and start to understand it’s use. They will find the app interesting,
recommend the app and send and receive coins easily with no technical ability.