I almost always deadhead each morning. If the weather (and ground) is really dry, I like to leave them on until they dry a bit. I figure the plant can suck in the needed moisture. When we've had too much rain, I will definitely deadhead in the morning. No scientific strategy on my part, just seems somewhat logical. However, on some cultivars I need to deadhead in the morning so the new blooms don't get captured in a soggy spent bloom or gets stained from the spent bloom dripping color onto it.
As for scapes: I've often questioned (myself) if pulling them off too soon or even cutting them down may be letting in bugs and bacteria. I even wonder if it increases the spring sickness that I see in my gardens.
