I'm a software developer with 5 years experience over 3 companies. Within the last year a junior (brand new to the industry) has started at my current employer.

I believe he is an excellent developer, who always delivers and is skilled as solving complex problems. However I'm slightly concerned that he is possibly applying himself too much for the following reasons:

• He begins work approximately 2 hours before most (and is expected)
• In his free time he has developed an application that was clearly months worth of work that is specific to our employer

I and the team are completely greatful for all he is doing, and is clearly an asset to our team. However I'm worried that this is not sustainable.

I can almost see that he has the same enthusiasm that I had when I began coding for work, however over the years I've realised that extra curricular work not only doesn't progress your career, but eats into your all important free time.

The question I'm asking is:

Should I advise him to take things a bit more slowly? Or perhaps I need to learn from him and do more for my employer out of hours?