Quote from: bloss on December 11, 2013, 02:00:30 PM

Before I pull the trigger on one of these kinds of solutions, I need to better understand how to use the address correctly. My understanding is that when BTC is used from an address, then the address should not be used anymore for security reasons. If that is the case, then using a single address to receive funds is confusing to me.

Spending money from an address lowers the security of that address. But this difference is rather theoretical. A bitcoin address is basically a hash of the public key, which is derived from the private key, which is needed to spend coins. Both steps to go from private key to public key and from public key to address use cryptographic functions that are designed to be irreversible. When you spend coins, the public key of the address is revealed and included in the blockchain. If the functions that derive a public key from a private key are broken, this might allow an attacker to obtain the private key, whereas if the address is never used, the function that turns a public key into an address needs to be broken as well.

Since the functions used are widely used and well-tested, this difference is rather academic. For normal purposes, there is no problem using the same address repeatedly. Note that this does make it easier for others to track your Bitcoin-activity. Whether this is an issue for you, is up to you to decide.

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I prefer to use Coinbase to handle my spending BTCs. If I use a single address to receive funds within Coinbase, and that money is spent later, will the original address still be safe to use? Will Coinbase automatically handle that address safety?

Does Coinbase guarantee that your deposit-address will remain available forever? If so, it should be fine. Personally, I wouldn't use an online wallet for Bitcoin-storage, but that's a matter of opinion.

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Are there any other considerations I should understand before I spend money making a physical QR code address?

I would only order such a gadget for an address I control, not an address linked to an online wallet. Bitcoin-websites have the tendency to shut down out of nowhere from time to time and this would render your physical QR code useless.