I haven't had a problem yet, however I have only done stacking 3 times. If you are unsure just call your local SOF and speak to customer service and ask. ( that's what I did) Just found that printable snuggle coupon! I thought there was one but couldn't seem to find it, until now! gaaah I could have gotten an even better deal! Oh well it pays to do your homework I guess??? Either way I have lots of fabric softener now!