What I can never quite figure out is, why do some people have reds bleed and others not?
I use a lot of red. Other than baby quilts, I don't remember a quilt that didn't have at least some red in it.
I don't prewash, nor do I use color catchers. I wash when they are done, in a front loading washer with warm water. I've only had one quilt that had any bleeding that migrated onto other parts of the quilt - and that wasn't actually from the wash, it was from being sprayed by the long armer. (Who returned it to me folded nicely so that spot did not show. Note: Always open the quilt when you pick it up!). Washing a couple of times with Synthrapol removed all but the tiniest of traces; if you don't know where to look, you'd never notice it.
I'm not sure if bleeding has happened in the wash and just didn't settle back onto other fabrics (as is what happens with dirty laundry) as they were washed with regular detergent? In other words, if I had had a dye catcher, perhaps it would have caught any dye that is dispersed in the water as they are treated to do just that?
Anyhow - since the one that came back with a bit of spotting, I have randomly checked reds with a damp white washcloth, but have never had any more that have bled.
My reasons for not washing are three-fold. 1, I like the "crinkly" look - although I wonder if prewashing fabrics for bleeding would still allow this to happen, as it would still allow batting to shrink up. (Aside: for those who was due to allergies/asthma, do you also wash the batting then?) 2, I like the crispness of the unwashed fabric for piecing; if I washed, I would then have to starch everything before cutting and 3, I guess the easiest way to explain it is laziness... I don't want to do the extra laundry and pressing!