Got 2x S15 / 28TH from January and February.
Can't complain , no issues and hashing strong.
This is all very pointless unless you have hundreds of them.
If 'one' of the two you buy fails and 100 someone else buys are all OK, it simply says you were unlucky - only one in that 102 failed.
You'd need to find some large miner farm and ask them about failures otherwise it's completely meaningless.