So I acquired a bulk box of white mushrooms... handling/preserving question

Well, the tough thing about mushrooms is that typically you should cook them before freezing if you want to really extend their life. Steaming is probably the most common method. But depending on how you intend to use them, slicing and cooking in oil before freezing works as well.

If you want to refrigerate them, as long as they are clean and dry you should get a good week or so out of them, maybe a little more.

If you want to use them in soups, stews, etc you could always slice the up and lay them out on paper towels to dry. Once dried place in ziploc bags and freeze. They can even be thawed in water (which rehydrates them too) and used as pizza toppings. We often find marked down shrooms (losing their nice appearance) at our grocers and this method works well for later use at a MUCH lower cost.

7 pounds of mushroom will cook down a lot.
Sautéed for steaks, omelettes, fatty innards, cheese steaks etc.
Ever made creamed mushrooms?? So good.
Marinate and toss on the grill, add to kabobs...