It seems I can never have just ONE box of cereal open at any one time. Just taking a random inventory for the past month or so, I've had at a minimum 3 boxes of cereal open at any one single day.
Same with mustards. I always have a bottle of yellow mustard, Dijon mustard, whole-grain mustard, and at least one flavored mustard open all at the same time. Heck, sometimes I'll have two different bottles of the same type of mustard open at one time -- a squeeze bottle and a capped bottle. One for sandwiches and one for cooking. Go figure.
But with potato chips and pretzels I'm less (how do you say?) promiscuous. I open a bag, and I finish that bag -- no matter how long it takes -- before opening and starting on another bag.
Are you a one-box kind of 'Hound, or (ahem) a bit more adventurous?