I believe the 10 days is only a guide as to when it should have settled down. If after 10 days you put more equipment/extensions back on the line and they cause any kind of interference then the line speed will re-adapt. I have had this happen and as a result now have no extensions just to get the speed up. I can't have my sky+ box connected either or I drop to 2 meg over a period of time from the 5 meg I get without sky connected. I've gone through all the suggestions of shortests cable not near any sources of interference ,changed filters etc etc, both Sky and BT have also been involved. I have just given up and disconnected it all.

Mark.