If he has more work than people the options aren't to regularly expect your employees to work overtime or turn down work. The answer is to hire more people. After this many years in business the owner should have a handle on his turnover rate and should be staffing appropriately so that loss of an employee doesn't leave him severely understaffed for an extended period of time.

If those in your industry are finding it hard to attract quality employees then it is likely that your industry is not offering the proper compensation to attract those employees.