I think that the issue is continuous raises. Instead the raises should slowly decrease but also the expectation of time commitment should decrease. It should be expected that someone with 10yrs experience at the firm only spent 10 or 15 hours per week working. They are exponentially more efficient. If it's then not expected that the company pay more, then the tenured employee isn't seen as a drain on resources. Hell they could even get payed less. It think it is fair because it allows people to seek out more work to fill their time.