Even when the funnel is over I still give each player 0-level characters if they "find" them in the game. So there's always a bunch of cannon-fodder. It also doesn't make me feel too bad when I kill off a Yfew level 1's here and there.
Yes. I agree with BigIron but have taken it a step further.
Make the funnel ongoing.
Frees the DM for killing. Frees the players to keep loving the funnel. . No reason to destroy the love of zero when it is so easily amended.
I would also add : never run a game without zero levels in the mix. Make them dogs if you have to., but definitely include "finding" in every adventure. Maybe let the new zeros get the dead adventurers stuff and add some post-history as to why that adventurer's death meant so much to them. Brother? Friend? Mentor? Idol? Enemy?Lover? I can imagine a spell book having a longer history than it's owners.