How do I protect my paper wallet from use by a different human who has used a random generator? Since millions of people use Bitcoin and Bitcoin Wallets that use their own addresses use several addresses per day, it is obvious that generators can generate the same characters for the Bitcoin address multiple times. So please therefore simply tell me how one would prevent others from accessing or spending the coins that are stored at my paper bitcoin address.
"Improbable" is an understatement.

There are 2256 possible keys.  In the entire universe, there are estimated to be "only" 2100 atoms.

So the odds of someone else ending up with the exact same address/key as you is far, far less than the same atom, out of the entire universe, being randomly picked twice.

If you are worried about an address collision, here are things that should be more worrisome:


Gamma ray burst wiping out all life on earth.
Sun unexpectedly going Supernova
Rogue Blackhole swallowing the solar system
An asteroid hitting the earth at the same time as nuclear war breaks out.


On the list of things to worry about, an address collision just does not show up.



You say that "millions of people use Bitcoin and Bitcoin Wallets that use their own addresses use several addresses per day".  

  100 Million of people 
  100 addresses per day
  365 days / year
* 200 years
-------------
Less than 1 Billion addresses used in the foreseeable future.


1 billion is about 230.
Which means that in 200 years, the chance of a collision is somewhere around 1 in 2256-30 or, 1 in 2226, which is still way more than atoms in the universe.

You're easily safe for at least 200 years.