In Fire Someone Today: And Other Surprising Tactics for Making Your Business a Success [1] by Bob Pritchett, cofounder of Logos Research Systems, Inc., chapter 4: There Can Be Only One—Plan for Your Partner’s Departure covers the issue of cofounders. I highly enjoyed and recommend this book.

Here's an excerpt from the beginning the chapter:

When I was a teenager, I toured a factory and met its owner. Dreaming of having my own business, I asked him for the best advice he could give me. His response was two words: “No partners.” When I started the business I run today, I did not take his advice—I started it with one partner and soon added another. Starting a business is hard work, and having a partner made it a fun adventure rather than a lonely quest. We did everything together, from the paperwork to set up the business to sales calls to taking all of our meals together so we could work on the business every waking hour. We became best friends and worked well together for years. When the day came that my original partner decided to leave the business, though, we realized that our lack of planning had endangered the multiyear investment we had all made and had changed the nature of our personal relationships. There is no way I could have started the business or seen it grow the way it did without my partners. As much as I now believe that “no partners” was great advice, I know that a partnership is sometimes the only way you can launch and build a business. But if that is the case, you need to make planning the end of your partnership part of planning the start of it.

[1] http://amzn.to/2blPmmT (affiliate link)

"I often thought they and the team would be much better off if they found work somewhere else where either they'd feel challenged to develop themselves further, or where their current skills were good enough."

This echoes one of the chapters in Fire Someone Today, a book with a seemingly heartless title, written by the CEO of a Bible software company. They had an underperforming employee that everyone liked & no-one wanted to fire, so they moved him through different roles to find something that suited him. After moving him through the entire company with negative results, they finally conceded they had to fire him. The punch line: the employee flourished as soon as he was fired - his dream had been to join the ministry, but he'd worried about quitting a stable job to do so.

The rest of the book is pretty good, about 20 anecdotes from running a software business.

https://www.amazon.com/Fire-Someone-Today-Surprising-Busines...