Let me print my boarding pass long before my flight
I love online check-in, and printing your boarding pass at home to avoid doing anything but going to the gate at the airport. Airlines are even starting to do something I asked for many years ago and sending a boarding pass to the cell phone that can be held up to a screen for check-in.
But if they can't do that, I want them to let me to print my boarding pass long before my flight. In particular, to print my return boarding pass when I print my outgoing one. That's because I have a printer at home but often don't have one on the road.
Of course, you can't actually check in until close to the flight, so this boarding pass would be marked as preliminary, but still have bar codes identifying what they need to scan. On the actual day of the flight, I would check in from my phone or laptop, so they know I am coming to the plane. There's no reason the old boarding pass's bar codes can't then be activated as ready to work. Sure, it might not know the gate, and the seat may even change, but such seat changes are rare and perhaps then I would need to go to a kiosk to swap the old pass for a new one. If the flight changes then I may also need to do the swap but the swap can be super easy -- hold up old pass, get new one.
I could also get a short code to write on the pass when I do my same-day check-in, such code being usable to confirm the old pass has been validated.