I frequently have a change to a fabric selection... Thats how my stash got so big. The LQS near me has terrible lighting... so if its not a nice bright day outside to double check the colors... I can end up with a no so great choice . When I make a bargello that has over 18 or so fabrics I always buy 20 ... as I will get home study them for a few days .. repositioning ... and a few just don't make the final cut..
Most shops will take back cut goods. Many have a policy it has to be over 1 yard.