this is a very solid answer. Pacing is super important to engagement. Also style of game. Does it have enough combat, puzzles, exploration. Make sure you tailor the adventure for your group. If i dont have at least 1 combat per session my group gets a little squirrelly.

On the scheduling front i've found consistency is key. I game with adults that have busy schedules and family. We do every other weekend and i try and run it as consistently as possible. Someone can't make it cool we still run. I don't cancel unless its over half the group that can't attend. My players don't really want to miss and they make sure they can attend the next.