I'd much rather have quality over speed any day with in reason.

If say for example you have a book time of 5 hours and it took 6hrs i wouldn't really mind as i know what its like in the real world but if it starts to creap up then i'd not except it.

Whats the point to having a mechanci who can do it in 3.5 hours but then a day or to later it comes back just to find it was caused by the mechanic rushing and it takes 2 hours to correct.

Ok some might argue its still only 5.5hrs but then you've most likely got to either stop other work booked in or re-schedule work to accomidate your come backs so eithe way there's good/bad points.