I agree with most of that which has been said!
I often use breadcrumbs too. The plot takes as long as it does but breadcrumb scenes happen anywhere, anytime I need something to have happened that either was caused by the players' actions or was not prevented by them, or just happened. Those can involve random players and may never be picked up by them, or might.
The breadcrumbs draw new faces in, or bring the plot back to the attention of the player base, and make it clear that sometimes they have to act.