Prism99

The reason I would use hot water with Synthrapol is because Synthrapol, which is capable of removing dye bleeds from fabric, works best in hot water.

I would try to keep water temp to 120 degrees F., which is at the low end of hot. Medium dryer heat is 125 degrees F, so drying flat is often a better option than drying a quilt in the dryer. This is especially true of vintage quilts.

I have washed quilts in hot water and dried in laundromat dryers. These quilts are washed at most once a year. While the cumulative effects do add up eventually, none of my quilts is heirloom quality or vintage so I feel comfortable with this. I do try to wash only the first time in hot water, with Synthrapol, to get rid of any possible dye bleeds. After that I wash in warm or cold water, depending on how stained or dirty the quilt is (and I don't use Synthrapol if the quilt didn't bleed in the first wash).

Edit: In my experience, exposing a quilt to light is much more damaging than exposing it to heat by means of hot water and a dryer. Light degrades dyes more than most people realize. It think the current standard for light fastness of fabric dyes is around 70 hours of exposure to light. Direct sun is the worst, but all forms of light fade fabric dyes.