Zach Waugh of Giant Comet and Flint fame writes:

But even after I released Flint for iOS in late 2013, I was only making about half of what I would need to go full-time comfortably. Building apps by yourself is a grind, and I was starting to wear thin, so I decided to leave Giant Comet as a side-project.

A wonderful product, aimed at a passionate, niche market and it's still a struggle and grind to make it full-time.

On a different note, Jared Sinclair with advice for the creators of the superb Crossy Road, who he's afraid might go out of business...

https://twitter.com/jaredsinclair/status/538895800089468929

https://twitter.com/jaredsinclair/status/538896069204402176

https://twitter.com/jaredsinclair/status/538896350264705024

https://twitter.com/jaredsinclair/status/538896767514054657

So much about staying alive as an ISV now depends on intangibles far beyond your design and programming abilities.