  During the past years, overload at work leading to psychological diseases,
such as burnouts, have drawn more public attention. This paper is a preliminary
step toward an analysis of the work patterns and possible indicators of
overload and time pressure on software developers with mining software
repositories approach. We explore the working pattern of developers in the
context of Mozilla Firefox, a large and long-lived open source project. To that
end we investigate the impact of the move from traditional to rapid release
cycle on work pattern. Moreover we compare Mozilla Firefox work pattern with
another Mozilla product, Firefox OS, which has a different release cycle than
Firefox. We find that both projects exhibit healthy working patterns, i.e.
lower activity during the weekends and outside of office hours. Firefox
experiences proportionally more activity on weekends than Firefox OS (Cohen's d
= 0.94). We find that switching to rapid releases has reduced weekend work
(Cohen's d = 1.43) and working during the night (Cohen's d = 0.45). This result
holds even when we limit the analyzes on the hired resources, i.e. considering
only individuals with Mozilla foundation email address, although, the effect
sizes are smaller for weekends (Cohen's d = 0.64) and nights (Cohen's d =
0.23). Moreover, we use dissimilarity word clouds and find that work during the
weekend is more technical while work during the week expresses more positive
sentiment with words like "good" and "nice". Our results suggest that moving to
rapid releases have positive impact on the work health and work-life-balance of
software engineers. However, caution is needed as our results are based on a
limited set of quantitative data from a single organization.
