A BT docment (SIN498) confirms that DLM constantly monitors VDSL2 (FTTC) connections for the duration of the connection.
On installation, the connection starts with a wide open profile, with Interleaving completely off.
If serious errors are seen, DLM will take more or less immediate action. Otherwise, it should wait for 2 days before making any 'normal' adjustments.
There is no mention within the document whatsoever regarding a 10 day training period.
However BT Openreach do seem to make users (& ISPs) wait for 10 days before initiating an engineer's visit, possibly to ensure sufficient error count data has been obtained in advance.
From my own connection (when engineers have requested DLM resets back to a wide open profile) & from monitoring other connections, I have seen DLM regularly wait more than the 2 days before taking action & applying interleaving/lowering sync speeds etc.
It may just be coincidental that changing the cable was around the same time that DLM had decided to take some action & your resulting resync caused by swapping cables triggered the action.
However, having recently experimented with a similar length of 'high quality', shielded & twisted cable between the modem & master socket, I can confirm that my connection deteriorated until I swapped back to the originally supplied flat cable.
My sync speeds reduced by around 3Mb after a few days of a reduced SNRM when using the shielded cable & are still very slowly climbing back upward, following a couple of DLM initiated resyncs & a couple of my own modem reboots.
The only real way to know what effect DLM (or swapping cables) has had would be to connect an unlocked HG612 modem & log/graph the connection stats over a number of days.
Then swap cables back to the original cable & monitor the connection's stats for another few days again.
BT's IP Profile occasionally 'sticks', especially when the modem resyncs very quickly on the fly, as is usually the case when DLM takes action.
A router (not modem) disconnection/reconnection forces a new PPP session & also updates BT's IP Profile.
A modem reboot/power cycle also has the same effect, but too many reboots & DLM can detect it as a problem & take even more severe action, lowering sync speeds & increasing interleaving depth, also increasing ping times.
Theoretically, DLM should detect an intentional disconnection, especially if a prolonged period has elapsed before connecting again (say the one hour as mentioned by Anotherone).
However, we have seen that DLM on VDSL2 connections can be rather aggressive in lowering sync speeds etc. & very slow at restoring them when conditions improve.
I have seen it take many days, weeks or even months for DLM to restore previously high speeds, occasionally causing a capped/banded profile that needs an engineer's visit before DLM is reset.
P.S. FWIW, new Windows compiled programs are to be released very, very soon (possibly tomorrow) for monitoring VDSL2 connections using an unlocked HG612 modem.
A GUI front end is now included for adjusting settings, folder locations, scheduled logging/graphing, recording resyncs etc. etc. etc.
