MTBF of refurbished D stock - again

So now that there is a statistically valid number of refurbished D stocks running on the District Line now, has any sizeable amount of data accumulated with regards to the mean time between failures (MTBF)?

I'm curious to know if they are more/less/similarly reliable to the unrefurbished units, mainly in terms of how easily the fitters at UDPT and ECDPT can repair them when they do break...