Do you have reason to believe the company will see it the same way when things get tough? A lot of people think a relationship is strong, then they get The Talk one day and find out they were the only one who thought that.
I do, because I’ve seen behind the curtain how these decisions get made, at least here. (Given that a sizable part of business went to zero when tradeshows went away, we’ve been tested as a company in the last 12 months.)
Now, if I became no longer useful to them for whatever reason, I’m sure I’d get The Talk, but I don’t know why that shouldn’t be expected, normal, and OK.
If an employer pays Y for X, but gets X+1 for the price of Y, why would he then bump you up to Y+1 if they don't have to? You're communicating through your actions that this is an okay state of affairs. You might do a bit of that X+1 work for some time to give you leverage during EOY reviews, but that's because you want that salary bump. Whether it will actually result in one is a different matter.
Jobs aren't charity and business is business. There's nothing inherently noble about doing a disproportionate amount of free work for a profit making company, especially when you have other obligations outside of work. Believing it is noble is a kind of Stockholm syndrome. The very essence of companies is to provide a service or product for a price as a just exchange of goods. The very nature of your employment is that they need someone to help make the service or product to get the money they want in exchange for a just fraction of the profits. When employees stop caring about adequate compensation, this results in a creeping exploitation.
I don't do work beyond the bare minimum to not get fired out of a sense of nobility or self-sacrifice. I do it in part because I enjoy it and I do it in large part because it pays quite well for me and my family.
By all means, if you're being inadequately compensated or exploited, quit and find a new employer (assuming you're in software).
Now, if I became no longer useful to them for whatever reason, I’m sure I’d get The Talk, but I don’t know why that shouldn’t be expected, normal, and OK.