No idea at all now kitz
From mid 2014 until January 2015 there were no LOS or router resets. In January Sky flashed the (SR102) router specifically to deal with the g.INP rollout (it was already fully compliant with g.INP specs but as we've seen the BT side wasn't) - I'm 110% sure on the f/w update reason BTW.
Since then there have been four LOS during the wee small hours - all of which have been remotely initiated (I can tell that much from syslog output). These LOS are not being triggered by DLM (they last several minutes - longest is 14 minutes) so I can only assume BT are flashing/updating the ECI DSLAM. It certainly isn't any sort of physical maintenance (CCTV from the shop across the road shows that).
I think (honestly) we can give up on any hope of vectoring in the UK inside the next 3 years - BT are incompetent in comparison to even morons like Telefonica (and you know my opinion on them kitz) - and g.Fast is a pipedream for the UK.
Openreach needs to be removed from BT control ASAP but that isn't going to happen while Theresa May is hot to trot for a UK equivalent of the great firewall.