To water, not to water
I've seldom seen more conflicting advice short of a political convention. Drown them, make them grow. Too much water, you get crown rot. Not enough, they will be smaller next year. Let them dry out between waterings. They get damaged, drown them to help them come back. Too much moisture, you encourage slugs and other munchers, and critters will dig them up looking for water. To quote somebody, "water is the best fertilizer you can give a hosta." Feed them, don't feed them. Mulch them, don't mulch them.
There has to be a happy medium somewhere!
Seems to me you have to apply a bit of common sense, and realize that what works in Minnesota doesn't necessarily apply in Missouri, or Nor Cal, for that matter.
Ken's sandy soil will stand drowning, clay soil somewhere else or rich composty stuff will give you crown rot if you overwater.
Average soil doesn't need drowning, just a couple of inches of water a week for most everything is adequate in most areas except in extreme drought conditions, when you might need more. The best test is sticking your finger in the soil, regardless of whether it looks dry or not. If it is damp an inch or so down, it does not need watered. Even if the leaves look wilted, they do that sometimes in bright sun in the daytime to reduce leaf surface to evaporation and will perk up at night.
Seems to me you have to look at each garden on an individual basis, to see whether someone else's experience and advice applies to you. I have a couple of hostas that never get watered, even in the drought. They are fine, a bit smaller than the ones that get their weekly dose, but fine. The groundhogs don't bother with them, either. I would water the hostas a lot less than I do, if it weren't for the companion plants, ferns, astilbes, etc. that suffer if I don't. Sometimes I just give them supplimental hand watering rather than soaking the whole bed.
Speaking from my experience, I have found that I can save many a damaged plant with a couple or three applications of liquid root stimulator/plant starter solution. And water as necessary.