At what point would you put seedlings under a HPS light?

I've had casualties when I've put seedlings under a strong HPS light too early. Googling around says you're supposed to do it as early as possible to make the plant more used to that much light.

How strong is strong? With 600w HPS I'd suggest starting about 24 to 30 inches above seedlings until they have 3 sets of true leaves. Lower the light over next couple days to your desired height. Are you flowering from seed?.

What I do is,4 or 5 cfl's till they grow wider then my quart pots that I use (3"-4").
Then 400 hps about 2 feet first day or 2 see how they take it.
Then around 20 inches.
Then the 600 for last week or 2 of veg.