What daylilies don't appreciate is wet/dry cycling, so with a good, open-pored soil mix, they seem to do much better if there's a constant supply of water. Seedlings, in particular, will get to the point where the entire container is crammed with roots, and that's when it's difficult to water them too much. I'm not talking about flooding them though, with 4" tall seedling pots, 1/4 - 1/2" of standing water in the tray is good. When that's gone, I give them another thorough watering. A good yardstick is to have enough standing water to last about three days. Very small seedlings are more susceptible to over-watering, but once they get to pencil-size, or you can see that they're drying out rapidly after watering, some standing water will help a lot.
