If you order something on the website for store pick-up AND it says "Available In-Store", your pickup will be ready within the hour and if it's not you can still go to the pickup counter and they will grab it for you. Best Buy will hold all store pickup orders for 2 weeks before canceling your order. source: 2+ years employee
I bought something on Sunday and within the hour got a text that it was ready for pickup. I guess it depends on how busy they are.
I believe their policy is 48 hours, but you can always call the store to be 100% sure of that.
You can pick up late, I'm sure.
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