All things can break and if they break, they do so at the worst moment.
For anything that I do not classify as a range toy, I have spare parts and spare optics. All my handguns that have red dot sights, also have co-witnessed iron sights. My defensive carbine has a secondary sight system.
Oh, and I do have an extra car in the drive way most of the time.
While I have full confidence in the scope maker/rifle maker/car mechanic being able to fix my stuff if it breaks, I do not want to depend on their schedule for anything that is important to me.
To be clear, I do not have two Tangent Thetas with one sitting as a spare. I can't afford that. However, I can afford to have a $300 fixed power SS as a spare scope or something along those lines. It is not as nice as a Tangent Theta, but it is a good spare scope and is good enough to get the job done in a pinch. In practical terms, I have two SWFA SS 3-9x42 scopes I use as spares, simply because I happened to have them. They track true, stay zeroed and have been with me for so long they are a sunk cost.
If you think I am paranoid... you are absolutely correct.
ILya