Debatable. Personally I would not try to do a project that uses wifi on a cell battery. And if you don't need wifi then you have much better options that use low current not only while sleeping (e.g. nrf series)
But my main point which I should have included in the previous reply was - what does real time OS have to do with the project being run from a cell battery?
So my assumptions in the original question a number of comments above (in the context of the comment above it) were:
- something running regular Linux would be too heavy (though I don't know if that's really the case, especially if you only turn it on a few times a day on average for a little bit)
- adding the "OS" abstraction would presumably result in access to higher quality ecosystem of libraries than whatever is available on bare metal directly (as I assume some of those libraries depend on the "OS" for event handling etc.) - which was the complaint in the comment I was replying to
But like I said, I know very little about this area, so if any of this doesn't make sense, just ignore my comment :D