Like jelly beans, you can never have enough tubes lying around.
Maybe I should get two tubes, but have them delivered in a package like this:
Packaging is *very* important to protect the integrity of the tubes. I get my cycling packages shipped directly to the garage to avoid inspection and customs tolls that are imposed by "others" who might inquire about packages delivered to the front door. Establishing a positive and somewhat private relationship with your UPS person can be helpful.
You can buy individual tubes? I always get a case.