I've also seen it where the previous station would insert the "donut", lock it in place and THEN pull the T handle so that the lav would dump behind the donut. Not a very good surpise for the next station.

As for the seniority thing, I think the only reward you can have for your years of loyal service IS your seniority. DL's pay topped out at 10 1/2 years, so that's not much of an argument. I spent 33+ years with the company and rarely got any respect from all the junior folks, even though we spent those years making it the airline it was and NOW it's their turn.