A good business man would realise that his staff are his best asset and that over-working them leads to mistakes and ****ed off staff that want to leave, like in your case it seems!
4 short jobs each day is an achievable amount all plumbers will be capable of and it will earn a business enough to keep you employed. They get a good balance between work and home time, they don't feel they have to rush and quality of work doesn't suffer. That means we get more customers in the longer term and grow quicker.
I agree with you there and that's probably why I've had 13 jobs in 16 years, I always got fed up of rushing round like a maniac and not getting home until late most nights.
The one thing I do disagree with is 4 jobs I think 6 can be done easily during the day unless they go over an hour job then obviously adjust that accordingly.