Leaving aside practical problems like cost, should you buy three of everything?

One to use everyday at home for you and your family to gain skill and familiarity.

A second to remain inviolate in your BOB for disasters and emergencies.

A third to take hiking, camping to gain more skill and familiarity.

Perhaps rotating things that are improved by breaking-in.

where are you gonna park the other 2 boats...?

A worthy question, however intended. My best answer to date:

The kayak lives on top of the vehicle.

The inflatable pfd lives with the BOB / ditch bag.

Other than cars, I think I already have at least three of everything significant.

Until recently I even had four mountain bikes.

In the interest of financial survivalism, it would have been more prudent for me to have two of everything and invest the rest.

In gold.

I don't think you have to have three of exactly the same thing, I think in the current example having three means of transportation would be sufficient. Have a vehicle, bicycle and boat.

Me thinks that is not an entirely unreasonable proposal ... and its good for the economy!!

I've heard several people who have recommended that people buy at least two of Doug's PSP kit. One to carry and one to tear apart and get experience with.

BTW, I put one boat in the garage - actually a canoe, one in the barn, and the other in the horse trailer. We don't use the trailer for horses much.

haha. exactly.

Possibly true for some things, probably wrong for other things.
I suppose budget and use count as factors in the decision.
Future availability certainly counts (within limits as Izzy points out). If you expect to be able to replace something easily then keeping spares is not as critical, if you expect it to be hard to replace then having an extra one or two matters more.
If it is something important, hard to replace and easily lost then Nighthiker's formula becomes the "Orders of the day."

This strategy will do more to stimulate the economy than provide for your well being.

Buy good stuff, learn to use it and maintain it. When the crunch comes, you will be relying on a tool you know well and can use effectively.

In the normal course of events, you will upgrade and supplement a lot of your items - knives, flashlights, FAKs, etc. and you will obtain some useful redundancy. But you don't need to go bonkers....

Often times I find myself buying at least two of something I like, when all I really needed was one. I don't go crazy when it comes to having redundant objects, but I at least prefer to have a spare on hand. I think this stems from numerous Murphy's law incidents. Where, when something breaks or goes missing, it tends to be at the worst possible time. I figure if I don't have at least one spare, I'm not going to have any when I need it.