Re: How to maintain revenue
If we were in the habit of considering software "done", I'd be typing this on vi and uploading it using FTP to a bulletin board.
Software is never 'done' because it can always be improved upon. No company is going to stop developing their software, sit back, and expect to continue selling the same software for the next 20 years. Their competitors would put them out of business within 5.
The tricky bit is, of course, determining what constitutes an improvement, which can be very much a matter of opinion.