And I would make the point that a properly trained and equipped tech, should have no reason to exceed a _properly_ quoted rebuild.
break down each part of the rebuild and look that part of the job over correctly and completely, include extra time to grind off the slag from the smelter and pound off the concrete from the construction company job, have the tech come to the estimator if they run into trouble.
The gravy, tough to chew meat, as well as bones, should be shared between the worker and the company.
I once heard that 90% of all corporate problems were related to communication.
if the job is -allways- taking longer than expected, then we are not accounting for some aspect of the time.