That's not a bad idea. I wonder if companies do this today.

I expect cynical HN commenters would make the similarly snarky comments about how X company is only committing to Y time period.

Yeah, they would.

But if Amazon committed to Smile for 2 years, then they could say "We're re-upping our commitment for 2 more years" every 2 years, bringing even more PR for it. And when it ended, there would still be some outrage, but probably not as much.

Most people only "give" when the bells ring outside the stores their buying gifts for others, so they're already used to "giving" during a window.