Honest answer? I'm not a beleiver in the "my consciousness is in my brain" worldview. If my heart were removed, I'm not sure that I would be "me" anymore.
If that's your logic, it would cost less time and money to grow and maintain
each indvidual organ than an entire clone, if you really want one in reserve.
Maybe if you're only making heart/lungs/liver/kidney/eyes/intestines/testicles/esophagus/spleen/bladder/galblladder/pancreas...wait, this list is getting longer than you expected, isn't it?
But that aside, remember that internal organs are not the only things that might need replacing. For example, what if you lose a leg? Would be convenient to have a replacement, wouldn't it? But there's no way to anticipate what you'll need and only make that. The simplest solution is to make an entire body.
That is just plain silly.
Our worldviews are different. *shrug*
Think of
Dolly the sheep. Cloning...simple and no problems, right? Well, no she had all sorts of unexpected problems and was euthanized at half the expected age because of them. So we did it, we learned some things, and the next time we did it better.
But mistakes can be made. As I said, I would be extremely hesitant to take a chance that could effect the entire species for forever based on only what we know right now. At first Dolly the sheep seemed like a great success. If we'd started cloning humans in mass based only on that early success, we'd have created all sorts of problems in the long run. If individuals get replacement plastic hearts because they choose it an on an individual basis, I'm ok with that. Making it standard policy for everybody...not so much.
Incidentally, in the interest of not wasting both our time, remember that at this point we're discussing very specific hypothetical cases. Please don't ignore the context of the specific case and try to apply that to the entire discussion and turn this into a 2 page argument over misapplied context.