When Claire was little, I started filling endebopes full of fun things for our advent calendar. That was the first and only year I ever filled the envelopes early. Now we use open envelopes and only fill them the night before (or sometimes, hurriedly before the kids wake up).
Notice, Day 18 is missing. I guess we'll take a break that day.
We always do simple things for our advent calendar. Things like make hot chocolate or watch a Christmas movie. I'm a big believer in not adding one more thing just to add one more thing. The calendar is something they look forward to each year, as we wait to celebrate the birth of Jesus.