I've just fitted the stainless bobbins into discs that have done about 27k (according to the old receipts I have with the bike). One side was OK, but the other was a very tight fit and it may take a while before it 'floats' as it's supposed to. I don't think I could have done this without removing the discs, due to the tightness of the bobbins and the awkwardness of fitting the circlips on top of the wavy washers supplied. I had to put the circlips part way on, then 'tap' them the rest of the way with a socket. One or two of the circlips don't seem to have seated concentrically and will be replaced.
So maybe an original set of bobbins would be easier to fit.
In line with what Frank says, I expect the discs to wear out before the bobbin holes do. I doubt if I'll still have the bike by then anyway. Ebay is my friend and my enemy :laugh.