If you know for sure you need it, then yes the store is just a place to hold things for you for a fee. The capital can be used for investment (say T-Bill at 3.5% state income tax free), the living space freed up, and you can wait for a discount.
The permanent storage space is the biggest cost to me in my area. Storing all the spare would be an equivalent to upgrading or downgrading my house to a new size that cost an extra 600k for the space, or a personal storage space in a warehouse that cost $200 a month.
Most people likely aren't in that bad of a shape when things break if they are not going to flood your house and your condo downstairs neighbor. You can still microwave your dinner for a few days or bake in the oven, or grab a $70 microwave driving 30 mins to a store. Fridge can be a problem but there are plenty of old fridge on craigslist people want to get rid of just because they are remodeling. Buying used then get rid of it cheap is likely just a quick cheap rent that isn't going to break the bank and just a temporary garage storage instead of a permanent eyesore as a spare. We all know how to wash dishes by hand so it is not that big of a deal really.
Also one last thing: your warranty start when you buy it, and if you keep a spare in the warehouse for 5 years since new you lose all the warranty for nothing.