Several updates:
I just had a long talk with my Costco career staffer spouse, who has been a Senior Refund Cashier for a long time. I wanted to share these tidbits related to posts in this thread:
Regarding returning snorkel gear and such at the end of your Hawaii vacation: Items used in saltwater quickly show signs of use. So it's one thing to have it look unused, and another to have it look like it'd been in the ocean for hours. And it's not just in Hawaii. Costco has a computerized shopping history on every account. It is available to be reviewed in every warehouse, company-wide. They can tell what you bought, when and where you bought it, and what you paid. That is how they can take back an item for refund without a receipt. They can even print a new receipt for you, if needed. But take note: They can also see your returns - ALL of them.
What they've started doing is tracking (among others) Department 26 and 27 items, which is Sporting Goods and Garden. During the refund process, they will check to see if you've returned similar items like that before. If you have, they'll check the documented notes of why you were returning that item before. If you've returned snorkel gear (for example) previously, saying, "It just didn't work as well as I wanted it to," and now this year you're returning the same kind of snorkel gear again, saying, "It didn't work as well as I wanted it to," you'll set off some red flags.
They'll explore your account further, and if the return seems abusive or habitual, you're likely to get a visit from a Manager, who will point out your history of buying and returning that item like that. And then they will suggest something to the effect of, "This is the (X) time you've returned this item in this manner. Obviously, our sporting goods items do not meet your standards, and we strongly recommend you buy your snorkel gear from another company." You may still get your refund that day, but if you try it again, you may end up having your membership cancelled. They aren't trying to police the activities of their members, but they are trying to protect Costco from abuse by some unscrupulous members, and to continue to allow the generous policy for non-abusers.
As to returning liquor, it may be a state law thing. In Washington state, where I live, you CAN return alcohol. It may be that in California, or at least in the Bay Area, that you can't.
The "return timeframe" varies by item. It used to be there was no limit on returning computers and electronics. They changed it to 90-days, to stop abusers. They have now started the same 90-day return policy with major appliances. If you have a problem after that 90-day period, you'll need to take it up with the manufacturer.
How's this for a tale of abusive returns: A friend of ours who worked in the Kauai Costco told us about a couple who returned a huge set of expensive patio furniture after only a week or so. When the whole story came out, it turned out they had rented a vacation condo for their Hawaii vacation, but they hated the patio furniture that came in the unit. They bought this Costco set to use during their vacation, and then returned it as they were heading to the airport. She told us the Warehouse Manager got involved in that one, and the couple eventually got their refund. All I can say is some people have cojones made of solid brass.
Dave