you can always self check in at a kiosk & self drop it.
Ime the kiosk is auto programmed not to allow you to print tags too early but the agent has the power to check them even if they are not supposed to.
I recently flew southwest w/ a friend. His flight was scheduled for 8 am and mine was 5 pm to the same city. Hoping to get on the earlier flight I accompanied him to the airport where they directed us to the kiosk. My boarding pass printed but they wouldn't allow me to check bags and he couldn't get the kiosk to work so we walked up to the bag drop where the agent was annoyed that we hadn't already printed tags but begrudgingly printed first for my friend. His bags were overweight so we did shifted some stuff into my bags. When it was my turn the agent made a face slammed down her cup of coffee, scowled some more at her computer (אין עוד מלבדו! אין עוד מלבדו! ) and eventually slapped the tags on.
After clearing security the gate agent who changed my ticket was bewildered as to how I got my bags checked.