It seems Sigma lenses tops out at bottom. Or bottoms up at the top? Anyway, that's not the whole picture:

"It may just be us, but during the last year we’ve had an amazing increase in the number of repairs that went straight back to the Service Center because the repair wasn’t made correctly. About one in 20 repairs had to be done over, far more than any previous year.

If the problem was inadequate resolution it was one in 10 repairs. We had 8 lenses that required 4 or more trips to finally get repaired properly. Probably the most disappointing part was that 19 lenses were returned to us with a fingerprint or lubricant smear left on an inner element during the repair. I could name names, but our experience has been this year’s best repair service is often next year’s worst, and vice-versa, so it probably isn’t worthwhile. But man, do I miss Jamestown.

But back to the point: for purposes of the data above, if I lens went to repair 4 times before it was finally fixed, it was considered just one repair."