Unfortunately, not living forever is true. That's why I've been forcing myself to make time to work on the Spitfire and Black Shadow. However, how we derive enjoyment isn't the same for everyone. To paraphrase another quote often used in the context of motorcycling, it's not always the destination (a restored motorcycle), it's the journey (the process of restoring a motorcycle)."
I can fully understand why some people would be frustrated at having to spend 10 hours reconstructing a particular part. But other people (e.g. me) can derive great satisfaction from the end result of the same activity. A purchased reproduction might be functionally identical to a time-consuming reconstruction, but emotionally they aren't necessarily the same.