Worth noting I've had great success in presenting encounters against minions hordes. As they drop, just respawn their losses at the edge of the battlemap at the start of their next turn. If the party gets under pressure, set a short round limit for the reinforcements. Alternatively, treat them as a trap: once the players realise the horde is unstoppable, they start looking for a trigger to stop the flow. Some of my best encounters have been based around this, I think.
When you do this and the PCs get into trouble, are you ever tempted to say "Elf needs food badly."