I see it exactly the same way. If the cardigan still looks good otherwise with the patches, I’d also be pretty indifferent to whether they last forever. It's possible that the spot will get thin again after a few years. But a few years will have passed by then, after all. It would be a shame to throw it out just because of the two elbows, especially with cashmere.
I’m curious to see what the tailor can do. When you get it back, please let me know. I’d be interested to know if the patches are noticeable during normal wear.