I'll cut to the chase: If you have any kind of stain, no matter how light or how small - warranty void.
If you have not rotated your matress religiously - warranty void.
Englander's version of their 15 yr warranty - rotate your mattress 1/4 turn (even though this causes it to hang over the box springs on each side) weekly for several months. If this doesn't work they will offer to send you some extra padding to stuff between the box springs and mattress to stiffen the spots with body impressions.
Is this what I spent well over $2000 for for a King memory foam set??? I asked how rotating the mattress one half of a turn (which is what they recommend until they void your warranty and the the 1/4 turn suggestion comes out) solves body impressions when the bed is occupied by two people and one half of a turn puts those two people right back in the same body impressions. They didn't offer an answer to this question of course. I also was told by the retailer not to use a matress pad because this would affect the memory foams ability to conform to your body and provide support as it should. Well thanks to that suggestion, any light stain affords Englander the ammo they are looking for to deny the warranty and place the blame for their defective product on you. Of course the stain(s) have nothing to do with the body impressions (just as lack of rotating the matress 1/2 of a turn does) in this defective mattress but this doesn't matter to Englander because they already have my money. Customer service is not their strong point as they are very good at shirking any warranty coverage. BTW. they don't "replace' mattresses, they only offer to "repair" them. hence the reason any little stain will void your warrnty because they claim that for health reasons they cannot ask their employess to handle your mattress.
To sum it all up: spend your money with a company that bulids a better quality product and actually stands behind their product warranties instead of finding any reason to avoid admitting their product is defective when it truly is.