Many great open-source projects were build over evenings with just 2 or 3 hours per day. Also it depends on type of work. Most people could work on CRUD websit

Many great open-source projects were build over evenings with just 2 or 3 hours per day. Also it depends on type of work. Most people could work on CRUD websites for 16 hours a day. But some work require laser sharp concentration and drain daily energy in half hour. And working tired is about as smart as driving drunk. What could possibly happen? :-)