I have had my line upgraded to max from the 12th April but it has been losing sync up to 30 times a day. Then I noticed something yesterday and again today which may be of benefit to members on the forum.
My router was syncing up at around the 5000kbps mark and was staying in sync until my home phone started ringing, then it promptly lost sync and although reconnected immediately always had a lower speed.
I have found that the base station of my home phone interferes with the router and causes it to lose sync when the phone is answered.
I have now moved the base station to a different room in my house and have had no more problems with the router losing its connection.
So for folks with cordless phones, it may be advisable to keep the base station away from your adsl equipment as it definately causes problems, I just hope now that BT's line management doesnt think my line is crap with all the sync losses caused by the cordless phone base station.