There are several basic concepts in ABA (e.g., matching law; ratio strain) that allow us to predict the ultimate outcome of increasing the work-to-reinforcement ratio, and none of those outcomes are particularly good for any party. Increasing you work requirement beyond the contractual limit is not ok. IMHO, consistently working at 130% of minimum expectations without additional pay-off (e.g., tangibles such money or comp time, or more nebulous stuff like higher chance of promotion) is also not ok.
Let me give an example of how this should be handled. I'm in a similar situation in my current position. I do almost exclusively testing (neuro-developmental- evals). We are down a psychologist, with very high demand (I'm booking in December). I consistently work at 130-140% productivity. I am eligible for quarterly productivity bonuses increasing in amount (up to ~5% of annual salary per quarter) based on quarterly productivity amounts over 105%. I can also earn an annual bonus based on productivity that can range up to 20% of annual salary (amount based on personal productivity and overall agency financial performance). I set my own schedule of when to assess. I have recently increased the number of assessment slots per week to help meet demand, but will be reinforced accordingly. I also have the option to schedule at, say. 150% one week and 50% the next. I Have done full weeks with no testing just to breathe and catch up on stuff. In talking with my department head about the high demand for my assessment services (basically amounts to a public health crisis in my area) we have identified options other than me working harder for the same amount of money. One option is to adjust the testing practice and mission to be able to see more kiddos in the same amount of time (e.g., focus just on diagnosis and referral rather than diagnosis and treatment planning; focus just on younger kiddos who take less time). Other option is to do nothing different personally (ultimately, It's not my job to solve access to care issues by changing my schedule) other than focus on recruitment effort (that said- if any of you are licensed/eligible in MA and want a good gig, PM me). Me working more for the same amount of money never came up because a) my employer recognizes my value as well as the risks of losing one of the biggest producers in the company; and b) my employer recognizes that I'm not a fool and could leave tomorrow and generate revenue for somebody else if they treat me unfairly.