Think back to that very first time you set foot in Costco, BJ’s, Sam’s Club, or other warehouse store: Remember how your jaw dropped when you spotted that keg-size jar of peanut butter, or that lifetime supply of socks? Bulk products at big-box stores have a gravitational pull on us all. Blame it on human greed, or American capitalism, or just our insatiable drive for a deal—after all, at that size, we must be getting a bargain, right?

Sometimes, yes. But not everything you see in these warehouses is worth the money or real estate in your already packed pantry. To help you separate the smart purchases from the space and money hogs, check out this antishopping list of items you may regret buying in bulk.

1. Things you don’t use often

Five years ago, Costco shopper Lillian Small got suckered in by a 1,000-count box of Q-tips. And guess what? She’s still up to her ears in those cotton swabs today.

“I gave half of them to my sister-in-law, but I still have the box,” she admits. “It’s moved from Canada to Paris to Scotland, where I live now.”

Lesson learned: Before you bite, ask yourself how much of this item you use per week. How about  per month? Then do the math to see how long that 1,000-pack will last.

2. Things that get ripe—and rot

Costco veteran Greg Schwem in Chicago admits, “I do pat myself on the back when I finish a 500-pack of coffee filters. For some reason I feel like I accomplished something.” But he’s still traumatized from the time he went overboard buying bags of apples, tomatoes, and other fresh produce that didn’t stay “fresh” for long.

“Even the largest Italian family can’t consume that many tomatoes before they go bad,” he says.

Lesson learned: On perishables, the clock ticks too fast to buy in bulk. Plus, that orchard’s worth of apples may not even be a deal.

“Citrus, onions, and bell peppers, in particular, are often more expensive by the bag than individually,” says Teri Gault, CEO and founder of TheGroceryGame.com. For example, loose onions often go on sale for 99 cents per pound. The 3-pound bag is $3.49 on average.”

And even if a food you’re itching to buy won’t perish soon, its quality may suffer. As Shwem admits, “I’ve tossed condiments like ketchup and mustard, which acquire what I call the ‘Costco crust.'”

3. Snacks you might get sick of

“I’ve been looking at the same stash of Clif Bars from Costco in our kitchen for five months now,” confesses JoJo Gutfarb of Walpole, MA, who picked up the energy snacks on an impulse.

Lesson learned: Beware of snacks you might love today, but tire of before your supply is depleted. Think: unique flavors of energy bars or potato chips (Lay’s Cheddar Bacon Mac & Cheese chips, anyone?). The combination of novelty and an apparent bargain is powerful bait many fall for, says C.W. Park, professor of marketing at the Marshall School of Business. Caveat emptor!

“But eventually, consumers will regret the purchase or throw it away,” he says. “It’s actually called the Costco Effect.”

To keep these impulse purchases at bay, write a shopping list before your trip—and stick with it.

4. Paper products (yes, even toilet paper)

“The one thing I’ve regretted buying in bulk are paper goods like paper, paper towels, and toilet paper,” says Michael Montgomery of Huntington Woods, MI, who purchased 10,000 sheets of paper, a 24-pack of paper towels, and a 30-pack of toilet paper. They sat in his basement for several months … until a flood turned them into a sopping mess.

Lesson learned: While you’ll use those paper towels and toilet paper, here’s the dirty secret: “You’ll get a better deal on those at grocery stores,” says Bob Shelton, a consumer consultant. Grocery stores typically run 20% to 40% off sales around the first and 15th of every month, since that’s when people get paid and generally have money to stockpile TP.

5. Exotic dinner entrees

When Melanie Downey of Leominster, MA, spotted a pillow-size pack of chicken pineapple meatballs at BJ’s, she thought they’d make an easy weeknight dinner. They were—for two days. But after that, her family was screaming, “No more chicken pineapple meatballs!”

“They’re delicious, but not something you want to eat all week,” she says. She considered freezing them, but “there wasn’t enough room.”

Lesson learned: Unless you have a backup freezer in your garage, avoid entrees that can be served only one way. Instead, dietitian Dana Angelo White advises buying a versatile staple like ground chicken, with which you can make anything from burgers to tacos to chili to meatballs.