I rarely place several orders with one vendor during a single sale promotion. I tend take my time looking over the entire inventory before making my selections and checking out. However, when I do, I never ask the vendor to combine the shipping and refund the excess...even if all of the items from different orders are placed into one package. IMO, it's unfair to expect a vendor to accommodate one's impulse purchases. While I am a firm advocate of a consumer's rights, I cannot support any endeavor that places undue hardships upon vendors. Honestly, if I were a vendor, such requests would drive me insane.
IMO, each party has rights and responsibilities. Merchants have the right to sell their products without being harried by a plethora of requests, questions and other forms of nagging from consumers in the midst of filling orders, especially during a sale promotion. They are responsible for the safe and consistent preparation, packaging and transport of their wares as depicted on their websites; they also have a duty to resolve all issues with minimal delay and outlay from consumers (e.g., no consumer should be required to submit fingerprints and two forms of identification in order to have a jar of spilled conditioner replaced...then have to wait 80 days for their replacement item to arrive). Conversely, consumers have the right to receive items as described by a given vendor that are free from dirt, hair and other hazardous materials and with a stable shelf life and in a timely fashion. OTOH, consumers are responsible for storing their items properly, in addition to exercising self-restraint by not having unreasonable expectations (e.g., don't hover over a vendor looking for tracking info only days after placing an order; not crying foul when spores arise after they've stored a handcrafted product in a muggy bathroom; realizing that combined shipping is a privilege, not a right so own one's impulsivity - either place one big order or bare the cost of the impulse purchases, which averages about $6.95 per order).
I view online purchasing as a partnership - consumers shouldn't have to jump through fantastical hoops in order to spend their money, and vendors shouldn't have to jump through fantastical hoops in order to sell their wares and build their businesses. Everyone has a role to play and fairness is a huge part of the equation.