My iPhone apps I created from 2009 - 2011 still provide a small income typically around $20 - $40 per month. Back in the day FemCal alone was doing $1500+ per month, with me 'full-time' on promoting and supporting it, but with little support or maintenance, apps waste away quickly.

It might be several hours to fix, retest and update documentation for even a small platform change, so just keeping up with platform changes can be significant effort if you work a full-time job, have children, other commitments etc.

The good news for me is that changes at work are affording me the opportunity to escape some process and re-open some of my side-projects again.

  * http://femcalapp.com