Techs who shows up every day, on time, ready to work....with high margins and few callbacks rarely move. I know. I've tried to pry a few loose from competitors over the years.
If they are all the things you state, then there is rarely conflict between the employer and employee.
Are there bad employers? I'd suppose so. But I have a hard time believing that an employer would abuse an employee that meets your stated criteria.
He would be a fool.