I have just had my line upgraded by
BT to a "theoretical" 8 meg line only to find that the line drops every 20 minutes or so.
After a couple of days of this I decided to call BT (the Mumbai version) and was told that this will happen for at least 10 days after connection to allow them to ascertain the maximum stable speed on my line.
This is all very irritating and what I find particularly galling is that they never wanred me that this would happen when I applied for the upgrade.