When there are people lining up to have your job, that's the way it should be. I've had to work 18-20 hour days for weeks on end in other countries. I've had to come in to work at 3am on weekends. I've been told at 5pm that I have to leave to fly somewhere at 6am the following morning. Those things sure as hell weren't in my job description, but I do it without complaining (before, during, or after) because I know that there are plenty of other people who would love the chance to take my job. Do I feel like I'm being taken advantage of by the man? No. It's just part of working the job that I have, even though it wasn't spelled out in the description.
And you are paid exactly what for your sacrifices?
I am happy to have my job otherwise I wouldn't have applied to work there, likewise my employer is happy to have me. Being happy and grateful has it's place but getting more and more uncompensated work dumped on you with the mantra "there are people lining up for your job" gets really old after awhile and it does nothing to boost morale or productivity.
If an employer needs to significantly increase my workload, they have the negotiated right to change the job description and bring it to the bargaining table where there will be dialogue between management and the membership regarding the fiscal need/justifications for such changes
how long such changes are anticipated to last and what compensations the membership can expect now or in the future for voting to go along with such.
In short, you're going to expect a lot more from me, you need to put that expectation in writing, I can then decide in a rational manner to stay or go
just dumping more and more on me over time while holding the club over my head about how many people want my job isn't acceptable.