There isn't a settling in period anyway, though BT Wholesale continue to say there is.
Openreach say that the line is connected at first with no limits (other than the product caps of 80/20, 40/10, 40/2) and DLM will not normally intervene until the day after first connection, as long as that first day's connection is for more than 15 minutes. After that it will do whatever it deems necessary for ever after.
I suppose therefore we could say there is a settling in period of the second day day plus the connection time during the first. Rebooting or disconnecting the modem a few times in that time-span could make the DLM either apply harsher stabilisation controls at the end, or in extreme cases even during the period.
My broadband basic info/help site - www.robertos.me.uk.
Domains,site and mail hosting - Tsohost
Connection - Plusnet
UnLim Fibre (FTTC). Sync ~ 53.4 (interleaved)/15.6Mbps @ 600m. - IPv4BQM