You'd have to clarify your question for a real answer. If you gave him tickets for stops further down on his route, and you just got off early, then yes he'd probably take them. However, if you handed a conductor tickets for the Capitol Limited, while riding on the NEC, then no he should not take them.

Additionally, as I mentioned above, getting off early would work. Getting on in Wilminigton heading for Philly, for example and trying to hand him/her tickets from DC to Philly should not work. Again, if the conductor isn't on the ball, then you might get away with it, but I wouldn't bet on it.

He/she should also not be accepting tickets for a future or past date either, but again if they were really busy and not paying attention, whose to say what might happen. Of course when they turn in all those tickets, it's also possible that the computer would reject them for being the wrong date.